General Web Resources:
Khan Academy: Khan Academy is a site with many instructional videos. You can search by topic or subject. The videos are very well done and cover wide variety of topics.
Geogebra: Geogebra is free software which is very useful for geometric constructions, graphs, and many other math applications. The Webstart button will download Geogebra to your computer. The Applet start will open a web based version of Geogebra but will not download anything to your computer.
Graph Paper: Embedded Math has many interesting things on its website including numerous types of graph paper.
General Math Help Sites
(Math help, information, and history)
This site has a little bit of everything. One feature that is found under both the "Mathhelp" tab and "Students" tab is call "Ask Dr. Math". This allows students to email questions to volunteers for extra help. Since these are volunteers, not all questions can be answered. However, there is an extensive library of previous questions and responses so you may be able to find a similar question to help get you started on your solution path. Dr. Math is just one small part of the site. The site contains a lot of information so don't be afraid to explore a bit to find what you are looking for. Since the site is so large, some of the information on the site is old but it is still quite useful.
This site has many lessons dealing with algebra topics. The lesson will show students examples with steps and brief explanations of the steps. There are also practice worksheets where students can choose a topic and then do problems. The worksheet has a place to type in the answer and then it will correct the worksheet after "enter" is pressed.
This site has lessons and practice activities. Using the "parents" link is particularly useful, even for students. Many topics are explained under this link by showing steps in detail and a brief explanation of the steps.
Most of the topics on this website are meant for students in Algebra II and beyond. This site has explanations organized by subject and topics. At the conclusion of a given explanation are some practice problems. There are also Cyberexams giving students a chance to practice. Another nice feature of the site is a message board organized by subject so you can post questions and get responsed from people running the site.
Math Explorations
National Library of Virtual Manipulatives
I have linked you to the high school version of this site, but clicking on the "Home" tab will let you access younger grades. The sites has many activities/games meant to help students practice and learn mathematics. The manipulative are organized by NCTM standards (the big "subjects" of mathematics according to the National Council of Teachers of Mathematics). After selecting an activity, there are many useful tabs at the top of the screen. The "Activities" tab has brief instructions for student about what they are to do. The "Parents/Teachers" tab explains the concepts students should be learning as well as some things to look for when students do the activity. The "Standards" tab takes you to the NCTM standards, which the activity is meant to help students learn.
This site is full of activities meant to help students learn mathematics. There are even several games of "Connect Four" where students need to answer a question before place a game piece on the board. Students are able to choose the connect four game they want to play based on subject. For example, there is an arithmetic version and algebra version among others. Students are also able to select from several difficult levels and time limits. Clicking on the activities link under the students part will take you to these activities.
History of Mathematics Sites
The MacTutor History of Mathematics archive
This site has a couple of very useful indexes. The "Biographies Index" has biographies about many mathematics in it. After selecting a particular mathematician, only a brief description appears. You can see more details by clicking on "Full Mac Tutor version." There is also a "History Topics Index". This features information from several different cultures. The site also has a variety of other useful and interesting information.
This site has articles dealing with the history of mathematics. One of the parts I found interesting was the "Regional mathematics" link. There were brief math histories of some civilizations. Parts of the site are still under construction so it should continue to improve and add information.