Well,
when I started with perl and Gtk on a thursday I only had the link to the well known tutorial which has been mentioned and linked above.
When I finished the application (about 1000 lines of code) on tuesday I had found
The Cookbook, was subscribed to
The Mailinglist
and studied the sources of
CSC Mail
which has a follow-up project called
Pronto (according to freshmeat) which I don't know anything about.