Ammentos is the lightweight persistence framework for Java. Highly probably the first one in the world available using JDK5 annotations. By far one of the most simple (someone says the simplest) to use: no installation required, no configuration, no external dependencies.
Ammentos is clean: no accessor methods required breaking good encapsulation, no interfaces to implement or base classes to extend making your design dirty.
Ammentos is plug and play: just put a single jar in your classpath and start persisting your model. Ammentos is a standalone libray: you can embed it indifferently in desktop applications, web applications etc.