Stardog is an enterprise-level triplestore developed by clarkparsia.com. It combines tools to store and query RDF data with more advanced features for inference and data analytics - in particular via the built-in Pellet Java reasoner. All of this is combined with a user experience that is arguably the best you can currently find in the market.

ClioPatria is a "SWI-Prolog application that integrates SWI-Prolog's libraries for RDF and HTTP services into a ready-to-use (semantic) web server". It is actively developed by the folks at the VU University of Amsterdam and is freely available online.

GraphDB (formerly called OWLIM) is an RDF triplestore which is used - among others - by large organizations like the BBC and the British Museum. I've recently installed the LITE release of this graph database on my Mac, so what follows is a simple write-up of the steps that worked for me.

Allegro Common Lisp (Wikipedia) is a commercial implementation of the Common Lisp programming language developed by Franz Inc. Allegro CL provides the full ANSI Common Lisp standard, but more interestingly for me, it also provides a very comprehensive suite of tools for semantic web programming. So I decided to give it a try. In what follows, I've put together some notes on how to get started quickly.