Google Service Notifier is a freeware utility for notifying anything from the various services provided by Google. As this application is right now in alpha stage, it supports google calendar as if now. It alerts you about the latest events and other scheduled meeting in your google calendar. It is a very lightweight and useful application that was designed in order to help you get instant alerts from google calendar.
Once you install this little application, it will start running in system tray and will notify you about any upcoming meetings and events in your google calendar. In future it might support google reader so you will get notified when ever you favorite web site feed gets updated.