The idea of not having to deal with storing your application's data has long been a pipe dream, but it seems that the folks behind the db4o object database have made it a reality. I've written a couple of posts in the past about db4o and how easy it is to use and it appears to be getting easier and easier with Transparent Activation and Transparent Update.
Transparent activation is basically just lazy loading objects in the object graph on an as needed basis. Transparent Update is the opposite; storing objects when they get dirty without you having to explicitly say so.
You can check out the press release on Transparent Update here.