The German game developers at Egosoft are currently hard at work on what very well may be the pinnacle of the 10 year old X game series. The new stand-alone expansion is called X3: Terran Conflict, and is due in the third quarter of this year.
If you missed all the other entries in the series, X3 is space-sim game, featuring dog-fighting, trading, exploration, building and other space-game type stuff. The last entry in the series, X3: Reunion came out in 2005. It received many positve reviews as well as a fair share of critiscm. On the postive side of things, the game was praised for having a terrific amount of things you could do in a open-world environment, with well-done graphics; on the negative side, many said the game was realeased too early, and could have been more fun.
The motto of the series is "Trade, Build, Fight, Think." This trailer below focuses on the 'build' aspect. Unfortunately, the trailer is only currently available via YouTube, so the quality could be better. Currently, the trailer has less than a 100 views, which perhaps does not bode well for the future of the series.
Personally, this gamer was intrigued by the previous entries in this series but never picked up a copy of the game. Perhaps this could be a good time to jump in however -- it looks like Egosoft built upon a great (however rough) foundation in the way of X3: Reunion, and just spent many months adding stuff and rounding out the game in all sorts of different ways.