My roommates and I share 1 printer. It was connected to my Mac and shared with their Windows XP boxes for months. We decided tonight to move the printer to the Windows XP router/firewall machine which is always on and never sleeps. But it didn't work ... after several hours of scratching my head, cursing, and perusing this site I managed to make it work with GIMP Print and the Windows XP TCP/IP Printing service hints. The results were very poor quality and taking forever to print. This was not good enough for us at all.
I finally stumbled upon step by step instructions for printing from an OS X machine to a not-PostScript printer on a Windows XP machine: How to Use a Printer Attached to a Windows XP Computer in Mac OS X.
I tried this with our Canon BJC-8200. It worked flawlessly, and only took 15 minutes to set up. Now my roommates and I can print from any machine in the house whenever we want, without having to run to the other end of the house, boot or wake the Mac, run back to hit Print on the document, then running back to the Mac to get the output from the printer.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030715035435755