A Mountain Druid can wild shape into giants. I think that's it as far as the ability to wild shape into monstrous humanoids, though, unless you and your GM come up with something homebrew.
There is giant form but that is unavailable to druids so that probably wont help you much. there is also giant hide armour, but you cant use the wild enhancement on that (not that you would want to use both at the same time). Finally there is the orc eldritch heritage bloodline that can make you go large for better bonuses but that is real late in the game and probably not what you are looking for. Those are the main ones that I can think of at the moment.
There's the monstrous form spell, that lets you take the shape of monstrous humanoids. I don't think it's on the druid spell list, though.
I know that this is thread necromancy, but on the off chance that it is still relevant and simply because I found it, here is the Mask of Giants that allows you to wildshape into giants. The lesser one only costs 15000 as well.
Edit: eh, this is only 4 days old, so no real necrothingamajigery or tomfoolery going on here.
