GWatchman

GWatchman is a free and open-source application for Windows. With this application, you can receive notifications for new unread posts on Google Reader and new emails on Gmail.

The application stays hidden in the system tray, showing only a discreet notification window when there are new items on Google Reader or Gmail.

You can regulate the frequency of updates and the way the notifications look from the application's settings window.

Besides all that, GWatchman also supports notifications for Growl for Windows.