Mars: Land of No Mercy, it was looking dead, but it's back! The website is back online and hopefully so is development. I would point out that it was always available on Sourceforge but an offline website can be a death knell for an open source game, so it's good to see things running again.
Ad Infinitum, a 2D space strategy game that looks very promising although is very early on in development and, other than the Sourceforge project page, doesn't have a website yet. It is also currently Windows only (Linux support done using WINE) but it is licensed under the GPL so there's always a hope that will change.
Whilst there's a few online space strategy games, there's not too many singleplayer Free Software space strategy games out there (FreeOrion and ?) so I hope to see this one establish itself. There's alpha releases available for download.
There's a new 3D artillery battle game about, called A3DX. The website, like the game, is in it's early stages of development. It looks very similar to Scorched 3D -- so much so that omebody suggested it was a fork but it's not. However, looking at the screenshots I'd say it's definitely not as Scorched 3D looks much more advanced (as is to be expected).
Hrm, what else...
The FreeCol team updated their website design - the previous design was over 5 years old.
No, that wasn't it. Erm...
Ah! ASC 2.0(.1) [Advanced Strategic Command] was released a couple of weeks ago. I think I missed it. This release is the culmination of years of work since the last stable series was introduced, and the community looks to be as strong as it has ever been. There's a multiplayer universe where you can pit your military wits against other players, and the AI isn't too bad either. There's a reasonable singleplayer element, although it's a bit short of being able to qualify itself as a singleplayer game. If the classic hex strategy games are your cup of tea, then definitely look at ASC as not only does it draw on the classic Battle Isle series, but it also has several years of steady development. It's available for Linux and Windows.