If you just want to clean the surface of it, a damp (not wet) washcloth should do the trick. Though...PS3 controllers are wireless, right? I'd take the batteries out first, just to be safe.
If you really want to deep-down clean it (which I usually do when I buy used videogame consoles/accessories), you'll have to take it apart. I literally do put safe plastic parts in a sudsy bucket of warm dishwater and scrub them down, toothbrushes wook good for heat vents and the like. I dry them off as best I can and then leave them to dry the rest of the way overnight (or longer if need be).
For the internal components, I'll usually take a q-tip dipped in rubbing alcohol to it and let it dry. It'll leave streaks though, Idunno, I've never been bothered much by it. Sometimes if a controller has seen a LOT of use, you'll rub a lot of carbon off of the contacts...Idunno if that's a bad thing or not, but I've never had a controller work WORSE after cleaning it...
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I'll brave the storm to come, for it surely looks like rain...