Freespace 2 is now available on Steam. The regular price is $9.99, but it's half off through the 13th.
Unfortunately, a number of people are reporting problems with the game, and are unable to get it to run. But Interplay has posted a note on the Steam forums indicating that they are aware of the problem and expect to have a patch available shortly.
On a nostalgia note, I glanced through the user reviews of this classic game and noticed one that made me chuckle. It consisted of just this one bit - "Hit your burners, pilot! Dive! Dive! Dive!"
Probably the single biggest wake-up call ever in the space combat sim genre.