I have been trying to get my iMac (Intel, 10.5) with both of my printers attached to share them since I installed Leopard. My two PowerBooks and my Linux box lost remote printing capability after the 10.5 upgrade.
My firewall was setup correctly, the printers were shared, and the laptops (now installed with 10.5) had CUPS browsing turned on like every other hint and discussion board posting.
After trying many things and reading many man pages, I found an old copy of cupsd.conf in /etc/cups/.
I read the following comment in that file about BrowseInterval, which Apple sets to 0 by default.
# BrowseInterval: the time between browsing updates in seconds. Default
# is 30 seconds.
#
# Note that browsing information is sent whenever a printer's state changes
# as well, so this represents the maximum time between updates.
#
# Set this to 0 to disable outgoing broadcasts so your local printers are
# not advertised but you can still see printers on other hosts.
#
BrowseInterval 0
I assume that Apple does this to stop laptop users from broadcasting printers while roaming (hint, if your laptop is sharing printers, don't forget to disable sharing when you leave home). So deleting that line changes the setting the default of 30 seconds. That, in turn, turned on Bonjour Browsing which allowed my 10.5 PowerBooks to connect and use the printers being shared by the iMac.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080229233456464