Printers that Work With Mac OS X?
Printers are easy, they mostly all work with Macs. Scanners are another story, and drivers for those used to be complex to find and use.

However 10.6 introduced far better support for scanners and a number of those now work just out of the box. I recommend you go for one listed as compatible if possible as an Apple maintained driver is more likely to keep working when you upgrade.

You can find the list of all printers and scanners supported out-of-the-box by Mac OS X 10.6 in this knowledge base entry.