I'm feeling a little nostalgic so I downloaded emulators for the Commodore 64 and original Nintendo system. Problem is, I'm having trouble finding games.

Anyone know a good source?

They're not technically legal, so legal sources aren't common.

Regular not so legal sources for other stuff has NES games available (every single one, in fact), not sure about C64 ones.

AFAIK, they are illegal unless you actually own the game.

EDIT - My bad about the 24 hour thing. Forgot to actually look it up.
It just depends on the company and the game. Some companies like Nintendo don't allow roms of their games, while others do.

A rom is legal for 24 hours unless you own the actual game.

It is not, the 24 hour deal has no basis in reality.

I could PM you the sites I know of but it is illegal to have ROM's if you don't own the game in most cases. Nintendo is still making money off of NES games.