Apple has posted a list of scanners and printers that will work with Snow Leopard

"To get software for printers that were not installed during the Mac OS X installation process, choose Software Update from the Apple menu, allow it to complete the process of "Checking for new software", and then connect your printer or add it using the Print & Fax pane of System Preferences. If software for your printer is available through Software Update, you will see a prompt asking if you would like to download and install this software. If you do not have access to the internet, you can insert the Mac OS X Install DVD and use Optional Installs to install the printer software available from the DVD."

For the list of supported printers, please see the following link.