EclipseLink last week released version 1.0. First announced at EclipseCon 2007, it was chosen by Sun as the reference implementation for JPA 2.0 at EclipseCon 2008.
Toplink has a successful history in object-relational mapping engines, and Oracle joined the Eclipse Foundation and donated the source for Toplink 10.1.3 to form the EclipseLink project. The goal is to have a standards-compliant persistence framework that can persist to multiple different back-end sources (SQL databases, XML files, legacy systems) using a unified API.
It is consumable as a library for standalone Java applications, or as a set of OSGi bundles for OSGi-aware modular systems. It's also possible to consume the libraries via a maven repository for those who use the Maven build system; and is included in GlassFish and Spring Framework distributions.
A webinar and introductory article are available if you'd like to find out more about EclipseLink, or you can subscribe to the team blog for further updates.