Google App Engine, which acts a Google-hosted application platform powered by Google technologies like BigTable and GFS. You can read more about it here. I was lucky enough to get an invite to try it out. Right now it only supports Python, but they say they plan on expanding this to other programming languages. I hope that's true. I never really played with Python but this might give me more incentive to take a closer look at it.
Anyways, going through their Getting Started documentation took about 10 minutes. All of the apps are hosted at the appspot.com domain but from the Admin console, it looks like you can have your use your Google Apps domain which is pretty cool.
Check out what I got so far at: http://notes.appspot.com