Once you have CUPS installed properly, you can easily print from both Unix and Windows clients. On Windows (at least Windows XP), open up the Printers list from the Control Panel and click on Add New Printer. Windows will ask whether it is a local printer or a networked printer.
Choose networked printer. From the next screen, do NOT choose browse the network. Windows will only browse the local windows network and will not show the CUPS server unless it is also running SAMBA. Instead, go to the box to type in the URL: