Sony should do a Virtual Console thing for the PS3. I don't believe the Playstation Network sells any PS1 or PS2 games? Think of how much more money they could be making if they made the back game catalog available online.
They sort of do...I wouldn't all it an "extensive" library right now though. Theres a few PS1 games you can get for the PS3 ans PSP, but I theres no PS2 games available. Though I suppose they probably could.