FlightGear:

Repositories for FlightGear:
deb http://debian.orson.at/repositories/daily/ experimental fgfs
deb-src http://debian.orson.at/repositories/daily/ experimental fgfs

FreeSpace2:

FreeSpace2 binary from cvs (joy-linux joystick support)

More Debian specific:

Debian info + repository (FlightGear/Mplayer/Widelands/Skype)