Snow Checker – Snow Leopard Compatibility Checker
http://snowleopard.wikidot.com/snowchecker

Still on the fence about upgrading? Check to see if your current software will be compatible with mac OS X 10.6 Snow Leopard, or check compatibility status before you buy new software. Snow Checker compares your current programs with the data found on snowleopard.wikidot.com.

Check out some other useful tools here: http://macshaman.com/get-help/tools/