I'm looking for some co-op friendly games...

...so my friend is moving off to Norway and we've recently been playing a lot of Resident Evil 5 co-op and really loving it. We were both trying to think of other game we can play co-op once he goes off to pastures new and I couldn't really think of any. So I thought I would crowd-source the question and see what you guys can suggest... 
 
We're both PS3 owners so that's what we would be looking at, as his PC is pretty old now and won't really be able to play much of the new stuff.

Borderlands is a pretty great co-op experience plus there are a ton of guns. Left 4 Dead 2 is fun if you like zombies.

Uncharted 2. Little big planet.

Demon's Souls.

I'm a big fan of Co-Op games.  I have a ton of them.
 
Unfortunately a lot of them are PC games or Xbox 360 games.  Going to have a hard time finding PS3 co-op.  But here are some of them off the top of my head.

• Army of Two and the sequel
• Borderlands
• CoD WaW and Spec Ops mode for MW2
• Dynasty Warriors (If you like mashing X)
• Rock Band and Guitar Hero
• Marvel Ultimate Alliance 1 + 2(I really liked the first one but I heard the second one pretty much blows)
• Raindbow Six Vegas 2
• Saints Row 2 (I fully recommend this one)

• Titan Quest/Diablo 2/And all the other Diablo clones out there
• System Shock 2 (If you can get it to work.  It's one of the best games of all time)
• Left 4 Dead and Left 4 Dead 2(Dunno the specs on your friends computer but these games run on a lot of older hardware)
• Killing Floor (Think Left 4 Dead but with a perk system from Call of Duty.  Weird but fun)
• Heroes of Might and Magic 3 (You can get it off of GOG.com for $10.  And it will run on Vista and XP with no problems)

" Can you play rockband online? thats a good party game "