For those who've been wanting to play Black Mesa, the fan-made recreation of Half-Life you're in luck as Crowbar Collective put up a Beta for Linux users.
For me, previously, the game just wouldn't launch since one of their recent updates. If you now opt into the "public-beta" on Steam, it should work once more. Really great to see Crowbar Collective get serious about fixing issues in their Linux build!
Full details here.
In regards to finally getting the Xen content update out, their Summer Update post talks about some really promising details. They're undergoing some external testing now, with most of the art being complete now.
It's going to be very interesting to play through to completion, since I did enjoy Half-Life myself, but like others I wasn't keen on the original Xen sections.
The game itself is also on sale with 60% off on Steam right now.