Originally Posted by
myrridin
If the above methods don't work, you could rig up a hydraulic press with a couple of car jacks and some pieces of 2x4 to slowly press the seat post out. You do have to be careful, since this method is able to exert enough force to break welds on the bike frame, but if they give first, I'm not sure the post would have been removable by any other method. You also need to be careful to use the same amount of force on both sides of the bike to avoid bending frame/post.
This might break the frame.
I would try the upside down -- stand on the seat -- twist the frame method. If that doesn't work, you're probably left with cutting off the post an inch above the frame and 'carefully' sawing a slot down the inside of the post. Then grab an end with pliers and twist it inward to break it loose. It's tricky to do.