PS3 is not region locked for games, however it is region locked for DVDs/Blue rays.
I have a US PS3 and I play Japanese games on it.
Not 100% true.
The old pre-slim model PS3s (60GB and 40GB models) are non-region-locked.
A limited selection of games have come out with region restriction though. I have a zone 1 (US) copy of Way of the Samurai 3 because I heard it wasn't going to be released here (eventually, several months later, it was). I can play it fine on my 60GB PS3, but my friend can't on his slim model.
MOST PS3 games are region-free, but not all. It's worth double-checking.