I've done MC, AQ20, ZG, ZA and Karazhan completely without too much of a problem (Pally + 4 Shamans).
I'd like to try Gruul and Mag to see if I can do it and perhaps some of the first bosses in SSC/TK. Once Cataclysm hits the shelf, that kind of places should be more easily doable. We might even be able to solo Kael'thas and farm Phoenix mounts

I've also done Noth and Patchwerk 5boxed because it was the weekly raid. No worries once you're in T9 and higher gear.