Gcal.app is a Google Calendar Client: "Gcal.app is a Google Calendar client for Mac OSX Tiger - a very minimalistic (WebKit-based) browser, that only displays Google Calendar. Nothing else. It’s meant to be as distraction-free as possible, allowing you to focus on tasks and events."
It might not seem that fancy but this little desktop/web hybrid application is good stuff. Plus, these hybrids can be made for pretty much any one of your favorite web applications. They can also be modified and extended to make the original web app better or different. Neat.