If you are searching on Windows for a nice system wide software to display notifications (like Growl for Mac) you will find Snarl (www.fullphat.net).
ThunderSnarl displays notifications using Snarl (has to be installed of course) for new incoming mails.
With ThunderSnarl 0.4 this extension can now be configured to avoid notifications for certain folders (e.g. spam, draft,...).
Also available in this project is a Snarl-extension for Firefox called FireSnarl for notifications about current downloads and an extension for Pidgin called PidginSnarl to be notified about chat messages and buddys signing on and of.