I clean my XD after every shoot, though she'll function well without any regular cleaning (I like to keep my carry gun clean, you know). I clean shotguns when I feel like it. Rifles using corrosive ammo are cleaned after each shoot, while those that use non-corrosive generally get cleaned every couple shoots.
My father, on the other hand, cleans his muzzleloader after each shoot, but doesn't clean any of his other guns very often at all. He kind of likes it when I borrow them, because they come back cleaner.