On: The Best E-Mail Program Ever: How Gmail destroyed ...

[ohhmaagawd]

A couple tips:

Gmail Notifier http://toolbar.google.com/gmail-helper/notifier_mac.html

This firefox extension gives you folders (among other cool features): https://addons.mozilla.org/en-US/firefox/addon/6076

[twopoint718 → ohhmaagawd]

Seconded, plus there is (at least one) for Linux as well:

http://gmail-notify.sourceforge.net/