If you are not familiar with db4objects ( DB4O ), it is an object oriented database. What does that mean? If I boil it down in laymen's terms : it is a database without tables or columns.
[...]
I did not have to do anything to setup how to save a User object in the database. It just serializes the object to the database. No need to worry about table names, column names or data types. This all comes for free with this engine, allowing a developer to focus on the domain model and the value-add code, rather than data persistence.
[...]
To help facilitate getting to software that can be demonstrated, I think that using a persistence engine like DB4O could really help with the time to delivery.
http://lostechies.com/blogs/hex/archive/2008/02/26/using-db4objects-as-a-prototyping-tool-part-i.aspx
(includes db4o related source code)