What web 2.0 tools are beneficial to Algebra?

As a math teacher, I am curious if there are a lot of Web 2.0 tool programs out in cyber land that are actually being used in Algebraic and Geometrical concepts. I have enjoyed the two programs that I shared on the class site, but I am wondering if there are math programs that are being used that truly enhance what I am teaching. In particular, are there any web 2.0 tools that deal with quadratics and parabolas?! If there are, I would appreciate knowing what they are!