Jena is a Java framework for building Semantic Web applications. It provides a programmatic environment for RDF, RDFS and OWL, SPARQL and includes a rule-based inference engine.
There is RDF data all over the place, in XML documents and sources like databases. Getting all that data is impractical, and would be unreadable (to say the least). So BrownSauce is an attempt to make something which can browse that information. BrownSau
RDF2GO is an abstraction over triple (and quad) stores. It allows developers to program against rdf2go interfaces and choose or change the implementation later easily.