Apple released new and updated Mac OS X 10.6 printer and scanner drivers for several devices on Monday. The update included compatibility fixes and additional drivers for products from Brother, Canon, Epson, HP and Lexmark.
To install the latest printer and scanner drivers, first make sure the devices are powered on and connected to your Mac or network. Next, go to Apple menu > Software Update to launch the Software Update application. If newer drivers are available for your printer or scanner, they'll appear in the available update list.
A full list of the printer and scanner drivers included with Mac OS X 10.6, or Snow Leopard, is available at the Apple Support Web site.

Jeff Gamet 

Yep - powered on; connected, but the new drivers didn’t appear in Software Update.
I had to download and install new drivers from the Support Web Site.
And then I had to go back to the Gutenprint driver for my Canon iP5300 because the new Canon driver doesn’t work. (Maybe Software Update is smarter than I think!)
Printer setup has been a pain since 1982- and still is sometimes.