I don't know if they've been discussed here before, but I have to rave about IsaBooties - http://www.isabooties.com
. They're adorable, super durable, they really do stay on, and they're vegan!
We can't usually afford to buy stuff like this, but we found a few bucks and I'm so glad we splurged. They're the only shoes Rowan (8 months) has worn for the past 2 months. He's a huge kid (already over 25 pounds) so he's outgrowing them faster than I would have expected, but I think an average-sized baby would easily fit them for 6 months or more. We'll be buying more for him to learn to walk in!
(ok, rave over. I have no association with this company, for the record. LOL)