Math

Dr Strazzullo

GeoGebra

Look at GeoGebra website for updated versions of the "installers" and for the GoogleChrome version, that works on portable devices.
New version, GeoGebra 5.0, has 3D graphics! 

Calculator

Extract all the files and run vti83.exe
This will emulate the TI-83 calculator on your PC.
 
A web calculator is web2.0calc.com.
 
A valuable resource is the CAS offered by Mathematica and the one on Desmos.
(.zip, 810K)
Download vti83.zip

MAT 099

MAT 102

Consider the free preview of chapter 1 and the free tutorials at www.interactmath.com.
(.pdf, 20K)
Download OLD Textbook TOC of 3rd Edition
MAT 099 students should use only section 1.
(.pdf, 519K)
Download SystemsOfLinEq.pdf

MAT 121

MAT 221

MAT 321

A Geogebra file you can use for various questions.
(.ggb, 11K)
Download 13Sp-Quiz2_17-GGB