Survey Companies (free to join and legit)

Here are the good companies that I currently use. You may receive spam if you sign up with the sites' sponsors, so it would be wise to set up a hotmail/yahoo account so your regular inbox isn't flooded with it. I still use my usual e-mail b/c I'd rather not check another e-mail addy and I don't complete offers from the sponsors, so spam isn't really an issue. I update this list of sites as I get checks from new companies.
I know it seems obvious, but the more companies you sign up with, the more surveys you'll receive. It's taken me over a year to compile this list and I as join more, more surveys come my way. If you only join one or two, don't expect to get many. It does take a while to sign up for the companies, so just take it a bit at a time. My bio isn't going anywhere :) Also, the more stuff you "do" in your house, the more surveys you'll get (usually). So, if you do the grocery shopping, maintain the cars, clean the house, take care of baby, make the financial decisions, make the buying decisions, etc., then you'll qualify for a lot more surveys. Do NOT pay to join a site.
Here we go....

They usually pay $3-15 bucks a survey. The surveys are pretty painless.

They actually put the money into your survey savvy account immediately. When you log in, click on "My Earnings" and then on "View Earnings" and you can request a payment of any amount that you've already earned. It takes about two weeks to get the check - I think they do it in batches.
Make sure you complete each profile in order to get survey invitations.

NFO/MySurvey Another great one that uses points that you redeem. WIth this one, 1000 points=$10. The way it usually works is they'll give you a screener survey for 20-30 points and if you qualify, they'll ask you to continue on to a larger survey. These usually start from 50+ points. Just an FYI - you'll get two surveys to start off - less than 5 minutes apiece. Only then will your account be activated. Be careful not to delete it as spam.
Mindfield Online (do product testing)
$5 is payout - they'll send you a check within 1-2 weeks. In each e-mail invite, it'll specify how much you get paid. It's usually $3-$5, sometimes more.
This is a good one. You get points for each survey ($2-$4 for each survey) and they don't last more than 10-15 minutes. 50 points=$5 and $5 is the cash out point. Points are usually credited to your account immediately after survey completion. When you refer people, you get 10 points after someone signs up and takes their first survey. Again, make sure you check your spam folder for surveys. You'll get a preliminary survey once you sign up (5 points).
They pay by check and usually have surveys related to recent public events.  They're quick and pay $3-$5 per survey.  I receive the check within 6 weeks.  If you take multiple surveys within a one-month period, they'll just add your pay together and send one check. Great company!
You qualify for online focus groups.  Sometimes they even send you a webcam to keep, in addition to the awesome compensation.  I've made $75-$150 per study.
This site sends a couple of surveys a month. They usually pay anywhere from $2-$5 each. Payout is after $5 via check, charity, or Amazon gift certificates. 
Fragrance Advisory Board Surveys are not often, but pay decently (about $1 for 5 minutes). Payout is after $5 via check, charity, or Amazon (exact same setup as the Socratic Forum).
They send out surveys frequently.  They range from $1-$5. Cashout is at $20 via Amazon, Macy's, Visa, and several others as a gift card.  You get the Amazon gift certificate immediately, but you have to wait for the others to be mailed out.
Here, you get to sample products from the General Mills team, and get paid in points for it.  1000 pts=$10 (paypal and online gift certificates).  I've gotten as little as $5 for a study, up to $100.
If you're a frequent reader of the newspaper, this panel is for you.  You answer questions based on ads you may have seen in a recent issue.  You get points for each survey (about 50 cents/points per survey).  Once you're reached 1000 points, you can cash out for a $10 Amazon code that will be e-mailed about a month later.
This company provides online focus groups. 
While the payout for each survey isn't that much (between 75 cents to $3), there are plenty of survey opportunites.  Cashout can be done pretty frequently for cash (Paypal), Amazon gift certificates, and other prizes.

They pay no less than $5 a survey - they're infrequent, but I just received a check - 5 bux is 5 bux! Yay!
They pay between $1 and $5 per survey.  Sometimes the surveys lead to a focus group or product test.  You can cash out at $10 with a check or Amazon gift certificate.
Harris Poll:
Another infrequent one, but you're able to cash out for gift cards.

American Consumer Opinion:
I get paid 6 or 7 bucks for each survey. They send out a check within a month after each survey completed.

Pinecone Research:
Unfortunately, you can only join this one via invitation when the company asks its members to send them out, or in a banner link. The banners are really hard to find. But if you get in, each survey pays $5 and it's usually about 15 minutes. The checks arrive within a week.

Test Spin
Point System - 1000 points=$1. I've gotten paid between $1 and $8 for each survey. They pay you via Paypal or Amazon Gift Certificates that they e-mail you. Payout is after $10. 
Survey Spot
They pay with points also.  100 points=$1.  Cashout is 1000 points ($10) via Paypal.

Brand Institute
This is aimed more for people in the medical field, but I got a couple of surveys for a few dollars each. A friend said she got several for $15 apiece and recieved her payment via check. They do require you to provide your social security number in order to get paid. They are also infrequent, but when they do send out surveys, it's usually for test products and they pay between $30 and $50.  Payments are via PayPal.  There are smaller surveys that they'll send out once in a while ($3-$5).

Harvard Business School
With this one, you actually have to check the site for studies. They don't send you an e-mail to let you know it's available. Usually a 15 minute survey yields $5, payable with Amazon gift certificates.

You accumulate dollars based on e-mails you read and quick surveys they send you. I don't get more than a couple of invites a week. It's really painless. You redeem the money in your account for airline miles, coupons from Hertz, Omaha Steaks, Blockbuster, and a bunch of other places. I usually redeem for magazines or Delta Skymiles - gotta save up for that dream vacation somehow! The only way to get into e-rewards is to go to the site and sign up under one of the sponsors saying you're interested. They'll send you an e-mail about a week later telling you how to join. I think they accept everyone though.

Resonance Research:

This site has only sent me one survey so far. But it just paid me $50 for 25 minutes of my time! You can request payment through PayPal or a check.

Toluna (used to be Your2Cents and Greenfield Online):
This site has a payout of $10. Payment is via check. They pay between $1-$5 a survey. If you don't qualify for the survey, they'll at least enter you into a drawing..
With this site, it's easy to get points. Each survey typically gives you 1000 points (15-20 min. long). You can cash out at 4500 points for E-gift certificates (4500 points = $5). After I cashed out, I got the e-certificate in less than a minute! (It says to allow 72 hours to receive it). Their referral program has ended.
This site is set up very similarly to Harris Poll. Surveys are infrequent. Points accumulate and you can redeem for gift certificates in different denominations.
Viewpoint Forum (do product testing)
With this site, you cash out at 375 points, which is equivalent to $10. They pay via check. Point values for surveys are usually at least 75 points. They do have a referral program (5 referral limit). Each referral earns you 100 points. I'm out of my referrals.
For this site, you need to check for new surveys...they don't send e-mails to you. Some pay with an Amazon gift certificate, or you can get an entry into a sweepstakes for a gift certificate.
Most of these surveys are for sweepstakes opportunities. But just like Survey Spot, I do the ones that guarantee a payment. 
1000 points=$50. Each survey is usually worth 50-200 points. If you don't qualify for a survey, you usually get credited 5 points. The check comes within 4-6 weeks. I've also tested a product for them. If you'd like a referral, please let me know.
Baker St. Solutions (do product testing)
Typically do product testing. You fill out a quick questionaire to qualify. If you do, you'll get the product. They don't let you know if you qualify for the study (like Pinecone). But they pay better. I received the $20 check within the specified time frame (6-8 weeks).
Click IQ This site took a while to rack up points, but the surveys are pretty painless. $25 is the cashout point (2500 points). You get an e-mail when there's a survey available. You do get 25 points if you don't qualify for a survey - but you know soon after starting the survey so you're not wasting time. Checks are sent within 8 weeks.  Referrals are available.
This site is a subsidiary of Lightspeed. They primarily cater to those in the tech sector of business. The hubby took a 40 minute survey and got $40 out of it. There aren't as many options for what to get with your points. But cash is king, right? :)  You can redeem for Amazon, Paypal, and all the other options you can do with Lightspeed.
There aren't a lot of surveys that come from this company. However, the online focus groups pay well.  I've been paid between $75 and $150 and I received the pay within a week of the study's close. If that happens only a couple of times a year, I'll be happy =)
These surveys are for points, to be redeemed for prizes. If  they're very short (it'll say the survey length in the e-mail), I'll definitely complete it because it usually leads to a product test. Who doesn't love free products? :)
You can get paid with American Airline miles, Amazon gift certificates, or PayPal.  You can take a survey once very 2 weeks, unless they send you a special invitation. There are online focus groups once in a while, too!
This company has short and sweet surveys on a range of topics.  Payment is by check and will come within 4-6 weeks.  They do ask for a social security number for payment.  I did a lot of research on the company verifying people's positive experiences with them. I was still a little leary, but it ended up being legit.  I'm sure some of you will still be uncomfortable joining, but I just wanted to put the company out there letting you know they pay.