Several of the games you get with the PS+ subscription have coop. Double Dragon, Scott Pilgrim, Ratchet & Clank, LittleBigPlanet 2, and now Dungeon Defenders. My wife is not a gamer by any definition of the word, and we are able to have fun with most of those games.
We also play LittleBigPlanet Karting together. I tried to get her into Awesomenauts but she didn't enjoy it.
There's quite a few awesome local co-op games on the PS3! Some of the ones I recommend are: Resistance: Fall of Man, LittleBigPlanet (1 and 2), Killzone 3, Ratchet and Clank: All 4 One, Motorstorm: Pacific Rift, and Mod Nation Racers.