Welcome to the world of gaming. Congrats on getting a ps3 . . . even as nothing more than a blu ray player it's well worth it.
If you're looking for a shooting game, Call of Duty 4 is just about the best thing out there. If you would rather something along the lines of an Indiana Jones type adventure game, Uncharted is regarded as one of the best games on the system. If you want something a little more animated, Ratchet and Clank: Tools of Destruction is what you'd be looking for. If racing is more your thing, check out Motorstorm. NHL 08 is also a rock solid experience if you're looking for a sports game. All games are very highly rated and look amazing in hd.
Don't forget the ps3 also has many downloadable games available from the playstation network (access it from your system). Games run about 10$ and there are some really fun ones. Highly rated are Super Star Dust HD (futuristic asteroids), High Velocity Bowling (probably don't need an explanation), Calling all Cars and Pain (not highly rated, but I adore it).
IGN is probably the largest gaming site on the internet, and for the most part their reviews are pretty trustworthy. Here is a link to ps3 games that have scored a 9/10 or higher:
http://ps3.ign.com/index/reviews.htm...ort.order=desc
edit: Just a quick thing that's a little OT. One of my favorite things to do with the system is to load it up with vacation photos (or any photos) and some good music. Play your music normally, hit the ps button on your controller (to go back to the main menu) and go view a slideshow. Your music will continue playing and you'll have a great way to show off photos when you have guests over.