Snow Leopard - Certain printers no longer supported
The best practice is to contact the manufacturer and confirm if their printer will work in Snow Leopard.
AppleTalk-only printers and printers that use PPC-only drivers are no longer supported by Apple.
If a driver cannot be found from the manufacturer, you can try to get at least some basic functionality by using a generic Gutenprint driver if its available. Be aware that some printer functions may not be available with these drivers.