A site with tons of example problem ideas for physics, math, and general science. Teachers can get ideas and students can get help.

An awesome site with games, logic puzzles, lessons, and so much more. Could be used in math or science classes with the logic puzzles. There are also conversions and much more.

Great web 2.0 site for math teachers. Lesson ideas, geogebra help, and exam view questions are just a few of the perks.

Great site with blogs, chatrooms, homework help, and so much more. Could be used in science and math.

A great site for finding random number generators and simulations. Includes dice, cards, number generators, and a lot more. Could be used in both science and math classes.

A free online graphing calculator. Much better than paying $120!

A great way for students to see the hazards and rewards of the stock market. Applicable to math and social studies.

Great site loaded with tons of free sound effects.

A great site on current events in mathematics and science.

Awesome site on the giants in history of math and science.

I know the way I set up the student, teacher, and lesson helpers (or resources if you prefer) was slanted towards math. I do think we make some changes to make it broader and fit any discipline. So for the teacher resources we could change math games to educational games or content specific games. The student ones are pretty broad (study guides, independent practice, tutorials) but there may be some that you guys would like to add. I'm sure there are other lesson resource groups you'd like to add. I just had data, multimedia, and graphing/simulations.

I just redid my classification system using inspiration. Like Carolyn, I used google docs as a means of showing the rest of you. Here is the link:
https://docs.google.com/leaf?id=0B0G8vlyB2rtTYjg5ZGM1MmUtZTY5ZC00MzJiLTlkMTYtYzczNTgzZjdmZDgw&sort=name&layout=list&num=50

I changed it into a pdf (since i used the newest inspiration as well) and uploaded it. This link should work.
https://docs.google.com/fileview?id=0B0G8vlyB2rtTYTNjNWQ0YjAtOWVmYi00NDg2LWJlOGMtMjg0NmNlZTY1ZWZl&hl=en&authkey=CIi6ydgD

When creating my Internet Classification System, I tried to work from the broadest categories to more specific ones. Due to the overlap in the subjects that I teach (many topics covered in Pre Algebra, Math 9, and Algebra II appear in more than one of the listed classes), I didn't want to separate based on the curriculum. The obvious choice to begin with was separating the sites that would be used for professional development and instructional use (as Carolyn did first). I felt that every site I'd ever use would fall into one of these two categories.
When deciding how to break down the Instructional sites I contemplated using the subjects that I teach but, due to the overlap in the subjects that I teach (many topics covered in Pre Algebra, Math 9, and Algebra II appear in more than one of the listed classes), I didn't want to separate based on the curriculum. I think tried to think of a way to classify the sites by some broad math categories (like using the NCTM or PA standards for mathematics), but many sites cover multiple categories. Finally I decided to break down the Instructional section into "helpers." This included sites that will help students (tutorials, study guides, independent practice, etc.), sites that will help me (pre-made assessments, printables, math games for students who finish assignments early, etc.), and sites that will be used to add to/complement my lessons (multimedia, data, simulations/graphs, etc.). This way I can limit the sites I'm looking for based on who/what needs the help. In other words, if a student says "Mr. Yates, do you know any sites I can go to for help on this?" I would be able to jump straight to the student helper section.
The Professional Development section was much easier to work with. My first category was Math Teaching Methods (further broken down into each subject I teach). This would be used if I wanted lesson ideas on a particular topic. Technology: I would include my SmartBoard sites here, along with any other educational sites covering current technological advances. Communication: I would go to this section when looking for ways to communicate with other professionals in the field (blogs, wikis, chat rooms, etc.). Finally, I wanted a section just for news regarding education. I called this Current Trends. These categories would cover any professional development site that I'd be looking for.
Creating a classification system is much more difficult than I would have imagined. It seemed like once a method was selected, you'd come up with something "better" and have to redo the whole thing. My goal was for quick finding of a site without too many labels.