Web 2.0 Table of Contents

I've often wondered how people keep up with the incredible variety of web 2.0 tools available on the Internet. Thanks to TechCrunch I've just found a new site called Simple Spark. One of the categories is education. Check out all of the tools available on this page.

Wouldn't it be interesting to challenge your students to develop their own table of contents for web 2.0? How would theirs compare to SimpleSpark? Since Web 2.0 is so interactive, you could even have students suggest improvements to SimpleSpark.
By the way, what is a table of contents?
Why should we categorize anything?
What in a student's life would be helpful to categorize?