Not sure if this one has been mentioned here already ?
I spent ages wishing somebody would put together a Battlestar flight-sim. And then they did. The team at hard light have now finished 'diaspora'. It's a free download too !
So how does it play ? Very good, surprisingly so. Good introduction/training to flying the Viper. Good controls. Good combat. On the whole it's excellent. At present there is only one single player campaign (about 6/8 missions) but there are third-party ones you can download and they plan on releasing 'official' add-on packs too. They've really got all the sound effects spot-on to give it a real Battlestar feel. Not just a space-sim. Definately worth a punt if you like sci-fi and flight sims
http://www.youtube.com/watch?v=DWt2m1xtJbw(Not sure of the video embed code for this forum ?)