Okay I admit, Google Chrome is not necessarily a productivity tool, it's a web browser, but I just had to mention it because it's my favorite. I haven't used it that long, but now that I've switched over it's hard to think that I'll ever go back.
Online Resources
There are so many resources available for teachers, too many to mention. Here are some of my favorites:
http://www.tammyworcester.com - Tammy provides wonderful technology tips for teachers
http://pagekeeper.teachingmatters.org/link/851/list - Bookmarks for teachers
URL Shorteners
This is especially handy if you are doing a presentation or sharing a website with students. Here are a few sites that can create short URLs.
www.tinyurl.com - allows you to customize the URL
QR Code Generators
Generate a QR code from any website your on. This is a great tool if you are trying a share a website quickly, especially helpful in BYOD classrooms.
http://qrcode.kaywa.com/ - plug in a URL and create a QR image that can be downloaded
http://www.activehistory.co.uk/QR/bookmarklet/ - Adds a bookmark button to your browser so that you can quickly create a QR image
"The beautiful thing about learning is that no one can take it away from you."
~B.B. King