The project leader of the Black Mesa mod made a official post on their forums today, letting us know that on September 14th you will see the first release of Black Mesa.
Originally Black Mesa, a Half-Life remake on the Source engine, was supposed to be released at the end of 2009, but the development team underestimated the work that was still to be done. Ever since then news and updates about the Source-Mod have been rare and rather small. Now it seems like the project is slowly heading towards its end.