gNotifier

gNotifier shows notifications for your GApps Services (GDocs, GMail and GCal). Click on a notification or the item in the dock menu to access it directly.
gNotifier will let you know when someone shares or modifies a document in GDocs.

It will also launch an alarm whenever a there is a reminder configured for one of your GCal events.

With gNotifier, you can know exactly what's going on at all times!