OpenCabinet aims to provide an easy-to-use library to store SQL-wise unwieldy data in a relational database. This includes collections, hashtables, and large binary objects. The focus here is on efficient storage and query capabilities.
OpenCabinet will also provide a simple solution for maintaining a revision history and audit trail for database updates, and a mechanism to implement long-running transactions similar in spirit to changesets in source control systems.
The project is still in its planning stage, i.e. there is nothing to download yet (except for the core SQL library that will be used).
While conceptually language and database agnostic, the initial release will target Java and Oracle (Hsqldb is used for unit testing).
The core OpenCabinet libraries will run on Java5 with no additional dependencies (except that you obviously need a database).