I'm not sure what it is about but Ko's Journey is supposed to be a great math game for 6th and 7th grade. http://dl.dropbox.com/u/3105141/C2CDN/Ko/content/educators_guide.pdf

Geogebra is bookmarked, haven't checked it out yet.
http://www.geogebra.org/cms/


Don't forget about youtube and Khan Academy.

Youth lives by personality, age lives by calculation. -- Aristotle on a calendar