As with all Hacks books, what you find here is just a taste of
what's most likely available by the time this book
ends up in your hands. Here are a few more resources you might visit:
The Gmail documentation (http://gmail.google.com/support) is
chock-full of tips, tricks, keyboard shortcuts, search syntax, and
more.
And, of course, you can always Google for gmail
hacks and gmailhacking.
Remember that all of these are hacks and, as such, have no quality of
service guarantees; if they break, they break. About all you can do
is go back to the hack's home page and see if
there's a new version available.