Well, it’s not hosting in the traditional sense, but it’s a fantastic resource, especially if what you’re developing needs to accommodate very large spikes in traffic. It’s called Google App Engine.

If you’re interested in knowing more about it and seeing a sample app I made (with video) then head on over to freesourcing.org and have a look. If you have questions you can post them as comments here and I’ll do my best to answer them.