Geogebra is open-source software that compares very favorably to Geometer's Sketchpad
Develop great skill in reading a ruler; A skill development game especially useful in middle school and Career Tech Ed Settings
http://www.rsinnovative.com/rulergame/
Brothersoft selection: Fractions; Parent help; Home schooling; and more
http://www.brothersoft.com/home_education/math/
CNET downloads: links to engineering and fincance applications; Maple 13 (not free), Reading math
http://download.cnet.com/windows/math-software/
Sage open-source alternatives to Magma, Maple, Mathematica, Matlab
[Win] software for extra help with basic algebra concepts. Features context sensitive explanations and templates for practice tests, exams, and homework.
[Win] publishes software for basic math, pre-algebra, algebra, geometry, trig, pre-calculus, and calculus. Solves problems with step-by-step explanations. Features graphing capabilities.
[Win, Mac, DOS] enables construction and manipulation of geometric figures.