New Site Address! http://blogs.msdn.com/b/jonathan_wise/

Cross Platform Printing

To connect and print to a Vista printer from Leopard, install LPR/LPD from Printing Features in the Programs and Features control panel in Vista. Connect the printer using the LPR path with the computer name (or, likely you'll have to use IP address) and printer share name. To add an LPR printer, you'll have to expand the Toolbar to show "Advanced."

To connect and print to a Leopard printer from Vista, don't bother trying the built-in stuff. Just download and install Bonjour for Windows, and use the Printer Wizard to add the Mac's printer.