Using Blogging in Math:

Darren Kuroptwa 

--the "king" of math bloggers;  example blog from one of his classes; includes many links to math sites

Google Sketchup

--3-D drawing tool from Google; can be used in conjunction with Google Earth

Fooplot

--online graphing tool

Road Sign Math

--Have students take photos of signs with numbers, then do math with them?  Check out this blog for ideas!

Chris Harbeck Presentation on web 2.0 tools for teaching math (from k12online conference)