The Jena Framework. Includes the Jena API, ARP, RDQL and DAML+OIL support.
David Megginson's RDFFilter package, with local modifications.
This is a compiled version of Doug Lee's concurrency package.
BerkeleyDB java interface. BerkeleyDB is available from sleepycat.com and is downloadable from here.
Testing harness from junit.org.