What exactly can you dual wield?

[Cyath]

I have a Warrior and a Rogue, and I know both of them can dual wield. The thing is, exactly what? I know a Rogue has to have a dagger in the main hand and sword in the off, not the other way around...what other permutations are possible? As for my Warrior, I tried to get him to dual wield two swords with no success. :(

I tried looking on the official Blizzard site but I can't find any concrete information about dual wielding...