The two that leap immediately to mind that are available on PS3, since that's what you said you own, are Heavy Rain and Bioshock. Both single player games, both amazing, and both unique experiences totally unlike any other game you could play. Bonus points for both since they have been out for a long time which means you can get them relatively cheap, which is good since you said money is an issue.
If you have access to a 360, I would highly recommend Fable 2, even if you have never played the first one. It is absolutely brilliant and beautiful, and once again has the added bonus of being cheap to purchase.
Also, it's old, but you can get Knights of the Old Republic (PC) on Steam for $10, and I would be hard-pressed to think of a better, more engaging game you can get for that price. Also it will run on pretty much any PC.
