For 4th edition there is not that much published yet, but there are some scenarios out there.
Adamant Entertainment has
Scourge of the Rat-Men, which is made for 4e (even though it doesn't say so officially).
Otherworld Creations has
The Forgotten Tomb of Felgar the Goblin King. A one night stand, as they call it.
Wizards of the Coast has only two official scenarios for level 1:
Keep on the Shadowfell, the first in their line of adventures, a pricey alternative which does give a bit of bang for the buck.
And in Dungeon there is the first adventure of their Forgotten Realms Adventure Path -
Rescue at Rivenroar. This is currently free to download, so a good alternative.
Goodman games are coming out with a couple of modules for Gencon, due to be in stores early september.
There are alos a couple of fan made scenarios, but both I remember were made by using the previews of the rules. Browse around the
4e Fan Creations forum and you'll find them.
Did I miss anything?