RGB filters for different forms of color blindness

My Google search came up with this one, which appears to be exactly what you're looking for. Eight different versions of color blindness are simulated by multiplying each of the R,G,B values by 3 different percentages and adding them together.

http://www.colorjack.com/labs/colormatrix/ (dead link)

Working Archived Link (working link)

I came across Color Oracle and thought it might help. Here is the short description:

Color Oracle is a colorblindness simulator for Windows, Mac and Linux. It takes the guesswork out of designing for color blindness by showing you in real time what people with common color vision impairments will see.

The GIMP has a colorblindness filter in View -> Display Filters -> Color Deficient Vision