Snow Leopard has several sources for scanner support. This Apple article lists scanners and printers that they have:
To update the support for those scanners, they have links for driver updates from these vendors HP, Ricoh,Canon,Epson,Brother,Lexmark, Samsung, Fuji/Xerox which if updated after August 28, 2009 for Snow Leopard. Most of these work through Image Capture as long as its preferences have TWAIN selected.
These other sources have scanners:
Exactscan has several compatible: http://www.exactscan.com/download/compatiblescanner.html
Some HP ones have a trick you can do as documented by this thread:
http://www.hamrick.com/ Vuescan has support for these scanners: http://www.hamrick.com/vuescan/supported-scanners.html
http://www.silverfast.com/show/snowleopard/en.html has Snow Leopard support for numerous scanners.