I had a mobile broadband modem hooked up to my MacBook and used it to get my Wii on the net by creating a temporary wireless network. I imagine the fundementals would be similar on any laptop. In dot point summary:
-connect your laptop to internet
-in network options (whatever it is called, probably under control panel) set up a network, call it something simple and, if you like, give it a simple password
-there should be some option to share your internet connection over this laptop, enable it.
-turn on PS3 and search for wirless networks, you should find your laptop and, voila! be able to hook it up to network and therefore, the internet
I know this isn't very details or specific, but I hope it helps!