This warning is implied in some of the other hints here on SMB printing, but I thought it might warrant a hint of its own ... If you use Printer Setup Utility (I've only tested this on Panther, but I would expect it to hold with Print Center on Jaguar as well) and you add a Windows printer, it will prompt you for a username and password to access the printer. There is a checkbox here asking to remember the password in your keychain. However, once you add this printer, the system will actually store your username and password directly in the URI in the /etc/cups/printers.conf file. For example, the URI path will read like this:
smb://username:password@workgroup/server/printer(this is what is implied by some other hints on this issue). Note that this file by default is only readable by root, so it only exposes the password to anyone who has admin access on the machine (technically, it's anyone with the root password or sudo permission). That may or not be acceptable on your system.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2004021704130820