HDMI cable would work, just hook it up and go to control panel => sound devices and change the output to HDMI rather than you laptops default, might be called SPDIF or something similar. Alternatively you could use a VGA or DVI cable for video, get a male-male 3.5mm audio cable (same size as your generic earphones) and hook that up to an input in a home sound system if you have one.
Alternatively, you could do what i do which is about a million times easier, and thats wirelessly transcode but that only works obviously for photos,videos and music. No games or if you want your web browser or whatever up there. But if it's just videos and stuff, get PS3 Media Server and if your PS3 and Laptop are running off the same wireless network it'll just automatically pick up your ps3, then go ps3 and i think its called DNLA servers or something. I'm not sure as i use it with my 360 i don't have a ps3 but yeh.