There is no escape...believe it or not. Mathematics is everywhere.
Here are a few free software programs:
R - statistical program --> link
SAGE - symbolic math environment --> link
Formulator Tarsia - equation editor & jigsaw activity creator --> link
Green Globs - Not actually free, but two activities. First game is points on a graph and students must use fewest equations to pass through all point. Second is game relating real world actions to graphs. Tracker looks interesting, but I have not tried it. link
Mathtrax - interesting graph tool suggested by a member of my PLN, although I have not had a chance to try it --> link
Note: many other tools at my Delicious account --> link
Some of my currents:
(1) I am exploring the use of MIT's Scratch as programming tool to model math (and TurtleArt as low-end intro to geometry)
(2) Grad work involves creating a collaborative and visual math environment where students discover numeric literacy and problem solving skills.
Geogebra and Formulator Tarsia would certainly be on my list. My other favourite is D.R.A.P.E. (Drawing And Programming Environment), which is a visual logo program which is great for kids to explore and learn angle properties in polygons. It was formerly freeware by Mark Overmars but proved so popular that it is now sold commercially by Sherston Publishing Group in a combined package called "Prof. Roberts ICT Problem Solving Kit".