If you're a heavy user of Google Docs but don't like constantly checking the site or email for new docs that are shared with you, Google Docs Notifier puts that recent activity handily in your Windows system tray.
Google Docs Notifier is really simple: you just install the app, log into your Google Docs account, and it'll start showing activity in your system tray. The system tray icon will let you know when new and unread documents show up in your account, and you can see your entire unread history by clicking the system tray icon. Clicking any document will open it up in Google Docs in your default browser. If you use Google Docs a lot, this is pretty handy.