Here's a resource that's free and open source:
GeoGebra
http://www.geogebra.org/cms/

There is a wiki where users connect: http://www.geogebra.org/en/wiki/index.php/Main_Page

Lots of free standing demonstrations like those at Henrico County Schools: http://teachers.henrico.k12.va.us/math/GeoGebra_Site/index.html

Best of all teachers and students can download the program and tinker with their own explorations.

I also have some geometry math links on my wiki at: http://cesa5mathscience.wikispaces.com/2008

We're holding a geometry week this summer as part of a math science partnership grant.