The new version of Ammentos Persistence Framework is available at

http://sourceforge.net/projects/ammentos

Ammentos is an opensource lightweight persistence framework explicitely
meant for JDK5 developers.
Extremely simple to use, it does not require any installation or
configuration files to edit; just a small jar file (of about 72KB) to
put into your classpath. Works whith annotations, what means compile
time checking of mapping declarations and the possibility to exploit
advanced IDE features such as code completion.

See here for more details
http://www.sourceforge.net/projects/ammentos
http://ammentos.biobytes.it