Liberated Games..

[mouser]

http://liberatedgames.org/

Liberated Games is dedicated to cataloging all full commercial games that have been liberated and made free in playable form to the public.

[zridling]

Okay, that's really, really cool. But where's Pong, damnit!

[jpfx]

underdogs has been my favorite for old games:
http://www.the-underdogs.org/

[PhilB66]

underdogs has been my favorite for old games:
http://www.the-underdogs.org/

Link changed to http://www.hotud.org/

[tinjaw]

Thanks for letting us know they are back!