Suikoden is a very good classic PS1 RPG that's available for $6.

My recommendations:

Toy Home. The game got slammed for the clunky controls (it uses sixaxis exclusively) but considering the whole point of the game is to smash into the environment, I think the controls work really well. There's a demo, so you can try it out. If you're going to buy it, I'd recommend buying the full expansion set, as it comes with a lot more cars (the monster truck alone is work the price of admission in my opinion) and some more tracks. Just don't expect Gran Turismo.

Rag Doll Kung Fu I picked this one up for free when Sprint was sponsoring it. If you have someone to play with, it's definitely worth it. And even for an antisocial gamer like myself, it's good fun.

Pain. Okay, so it's not really a game as much as it is a Havoc Physics demo, but it's good for a laugh. I don't recommend any of the expansion sets, though. I bought the theme park, which is kind of fun, and the movie studio, which is less fun. The city is the most fun of all the environments. Save your money for the David Hasselhoff avatar. You won't regret it.

I also have Noby Noby Boy, Loco Roco Coccoreccho and Trash Panic, but I can't really give any of those a full voiced recommendation. Noby Noby Boy is really thin, Loco Roco is really just a glorified screen, and Trash Panic is just too freakin' hard.

I guess it's kind of strange, since I've bought a FEW things on XBLA, but I've yet to buy a single thing from the PSN store. I think the lack of demos really kills it for me.

2 weeks since I bought my PS3. Only game Ive got so far, from either PSN or disc, is Flower Clearly the money was well-spent.
Flower is kinda neat anyhow.

Burn Zombie Burn.

I totally don't get all the flower love, but to each their own I guess.

I'd say try comet crash, burn zombie burn and fat princess. They all have demo.

There are a few gems in the PSN store but for the most I second the recommendation of sticking to disc game.

Try a demo for everything you can before buying.

WipeOut HD is an excellent racer if you like that kind of thing. I want to like it but sadly I'm not a big racing fan. I just really like the aesthetics.

Trash Panic is a ton of fun (it's a puzzle game where you need to fit a bunch of trash into a bin by smashing, burning, and careful placement). It's just BRUTALLY difficult and there are no save options, so you need to start from level one each time.

Warhawk is supposedly very good. Never got around to trying it.

Super Stardust HD is beautiful and fun, but definitely not for everyone. Try the demo and see what you think.

Echochrome has a neat idea and artsy execution. I didn't find it very entertaining, though.

I've heard Pain is good for a laugh too but I've also heard the novelty wears off very quickly and after that, there's just not much meat to be found. I suspect there's no demo for it because the full game is demo-sized. I've been unable to justify it to myself for $10 just yet, so I can't tell you if it's worth it or not.

If you are looking for action/adventure, be sure to check out both Trine and Ratchet & Clank: Quest for Booty. Yeah, they are both a little on the short and pricey side but still great games. Flower is another fantastic option, just as much an experience as a game and easily the best use of SixAxis. Magic Orbz (previously Magic Ball) is a breakout-style game with cartoony 3D graphics that's quite a bit of fun, too.

Other great stuff that don't necessarily fall into the casual category include:

* Shatter (possibly my favorite downloadable game across all systems)
* All of the PixelJunk games (Monsters -> Shooter -> Eden -> Racers)
* Super Stardust HD
* Trine
* Burn Zombie Burn
* Zen Pinball
* Critter Crunch
* Wipeout HD

-Critter Crunch is by far the best value on PSN today, bar none. The game is addictive & stylish. It sports a single-player adventure mode that is both varied and beefy. Though we each have our own PS3 profiles and adventure mode game saves, my wife and I love playing levels hotseat...helping each other through the more difficult challenges.

There's a demo for it too.

-Wipeout HD/Fury is a bit pricey ($25 for the combo pack of HD/Fury) but I think it's the best "full retail game experience" on PSN. Must-own material for fans of the genre/franchise.

Though not exclusive, download Burnout Paradise if you don't have it already. I think it's only $20 on PSN, and it's a great game whether or not you like racers.

My wife and I also play a lot of Pixeljunk Eden. We finished the main game together, and are about 2/3 done with the expansion pack. It's a good coop platformer but it can get tricky and tedious at times. We managed to figure it out without any FAQs, and minimal bickering, though. It'll keep you busy for several hours if you enjoy the game, and it has a demo that allows you to play up to 3 players on one of the maps.

Critter Crunch is fun and beautiful but the difficulty really ramps up drastically toward the end. It's getting a patch to scale down some of the more difficult puzzles, but we'll have to see...

If you want an action game, Battlefield 1943 or Fat Princess should do the trick.

I agree with everyone who said try before you buy. That's what those demos are for.

That being said, I heartily recommend all the Pixel Junk games, they're fabulous. Also, Super Stardust HD is still one of my favorite PSN games. It easily gets the most workout in my house of all the PSN games I've got. Lastly, if you've got a PS3 Eye, get Aquatopia. Coolest virtual aquarium ever.

I believe it is in the UN charter that once you buy a console, you must also buy that platform's remake of Classic Bomberman and Worms. And who are you to thwart the UN?

If you like puzzle games, I wholeheartedly recommend Trash Panic.

It's a very neat physics based game where you're trying to pack trash as tightly as you can by breaking it apart, burning it or letting it decompose as you get into the later levels. Check out the Giant Bomb Quicklook if you want to see it in action.

(Oh, and if you do buy it, you should play through Easy first, and then try Normal.)

Gravity Crash is also pretty cool, and there's a demo for it.

And I also recommend Critter Crunch, Pixeljunk Shooter and Flower.

Ditto Fat Princess, Flower, Pixeljunk Shooter, Eden, and if you aren't web/iphone tower defense gamed out, Monster.
Trine, Wipeout & Superstardust are decent too, but not as much my "thing" as the others. Nobynobyboy is a weird thing which isn't much fun as a game, but if you're into weird arty things, it might be worth checking out. It's pretty cheap if I remember correctly.

Here is what I recommend of the exclusive titles...

Calling All Cars - Fun local multi-player with up to 4 people.
Super Stardust HD - Best two stick shooter on PSN IMHO.
Everyday Shooter - Cool two stick shooter, with great audio integration, really hard.
Pixel Junk Monsters - Best tower defense game I have ever played.
Pixel Junk Shooter - Physics puzzle two stick shooter.
Ratchet and Clank: QB - Great game short but sweet.
Trine - Awesome side scroller, physics puzzler.
SOCOM - Good multi-player shooter.
Crash Commando - Sort of like a side scrolling unreal tournament.

Other people like these me not so much...
Fat Princess - Cool idea, gets old quick, like after 15 minutes quick
Blast Factor - Good game, not as good as SSHD and Everyday Shooter.
Flow (I assume Flower is similar) - Interesting, artsy, original, and absolutely boring.
Echochrome - Played demo not really that great IMHO some people love it.
Locoroco Cocorecho - Not anything like the Locoroco on PSP, in fact I have not idea what your supposed to do in it.
Pain - If you really like Jackass and/or physics demos then you may like it, otherwise i'd pass.
Warhawk - I didn't like the mechanics at all, very floaty and arcadish, the best feature of the game is split-screen co-op online.
GT Prologue - No real reason to get it at this point, and the price is too high.
Wipeout HD - I didn't see anything special about it, seemed like a newer version of the old ps2 pod racer game.