Kwerty Gmail Notifier for Windows 7 monitors your Gmail inbox and notifies you of new emails. It takes advantage of the latest Windows 7 UI elements such as the taskbar overlay icon, jump lists and thumbnail previews. It's fully compatable with Google Apps accounts too :)
Here are some screenshots:
The standard taskbar icon
You've got mail taskbar icon overlay
Thumbnail previews of new email
Jumplist for common tasks
Head over to the website to download Kwerty Gmail Notifier