Technically speaking, all of these are still in print or are being reprinted in the near future in some way:
Paranoia (new version coming out soon)
Space 1889 (currently in print from Heliograph Games)
Traveller (Original recently reprinted, GURPS and D20 versions still in print)
MechWarrior (currently in print from Fanpro/Fast Forward Games)
Abberant/Trinity (White Wolf Games-D20 versions due out soon)
These are TRULY out of print as far as I know:
Melee/Wizard/In the Labyrinth (Metagames/Steve Jackson Games)
Prime Directive (Task Force Games)
Brave New World (Pinnacle)
Underground (Mayfair)
Paranoia (new version coming out soon)
Space 1889 (currently in print from Heliograph Games)
Traveller (Original recently reprinted, GURPS and D20 versions still in print)
MechWarrior (currently in print from Fanpro/Fast Forward Games)
Abberant/Trinity (White Wolf Games-D20 versions due out soon)
These are TRULY out of print as far as I know:
Melee/Wizard/In the Labyrinth (Metagames/Steve Jackson Games)
Prime Directive (Task Force Games)
Brave New World (Pinnacle)
Underground (Mayfair)