canning jar travel/sippy lid has been great while he learns to hold cups correctly. It isn't leak-proof, but it certainly minimizes what otherwise would be a major spill down to just a dribble.
So far so good really on the weaning front, he hasn't asked for a sippy cup once. I just have to be aware of the amount of straws we have on hand. I try to wash the plastic "disposable" ones and reuse them, but sometimes they're just a little beyond repair (read, he chews/crumples/smashes them). Metal straws are certainly handy and not (easily) smashable, I might have to get some more of those.