T.G.
M.,
My son drinks out of the NUBY sippy cups from wal-mart or target. You can get them at both. He is constantly throwing them on the floor or couch and they don't leak. (Unless they get slammed down really hard - messy)
I tried a bunch of different kinds and these seemed to work out for us and they are not expensive at all. I think they were around $2.00 each??
Hope this helps.
T.