Cairn of the Winter King from the Monster Vault is also nicely put together. If you like things deadly, some of the fourthcore adventures are great, like Crucible of the Gods.
Really, though, I think the best adventure to introduce 4e is one of your own. Seriously, give it a try, it's a really DM-friendly edition and I bet you'd do well. There's certainly more ownership and, by default, personal investment.