I was looking at some of the previous hints and did not find anything useful as far as printing to a shared printer (CUPS) in Linux. I have an old Pentium that is set up as my Samba / share / printer / etc. Currently, Windows can print to it fine via Samba (check the docs - with newer Samba versions, it requires adding two lines to the smb.conf file). As far as adding the printer to your Mac (OS X 10.2.6), it's really easy (after you figure it out). Start by going to http://localhost:631/ with your favorite browser. Go to the Administration section and click on Add Printer. On the first screen with Name, Location, and Description, most of this is irrelevant. Pick a name, enter some descriptive info, and click Continue.
On the next screen, click the Device pop-up menu and select "Internet printing protocol (http)" and click continue. On the next screen, for the Device URI, enter http://192.168.1.1:631/printers/deskjet. Of course, you'll need to change the IP and name of the printer (mine is deskjet) to match your setup.
Then, make sure you select a driver that matches up with your printer, so you can change some of the printing options. I'm using a DeskJet 3420. Really inexpensive and works great.
Hope this helps someone out.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030929132147600