Someone in the comments at tenfootpole.org was lamenting that there is no central resource for good free OSR material, and it occurred to me that this would be a good way to introduce 4e players to a different approach to gaming. So here is a starter list, more or less by order of level, pulled mostly from “The Best” category at tenfootpole.org.
The Prison of the Hated Pretender – level 1, 4e lower heroic – The link also includes a number of other decent adventures by Gus L, including links to the reviews, so check those out as well – Reviews: Bryce Lynch
Gone Fishin’ – level 3ish, 4e level mid-heroic – I’m hoping this is still free, it was when I got it, but the original link has disappeared, and I’m not sure if this link is official – Reviews: Bryce Lynch
Challenge of the Frog Idol – level 3-6, 4e mid to upper heroic – while you are at it, check out Dyson Logos’ maps, which you will find on the left-hand banner – Reviews: Bryce Lynch, Peter V. Dell’Orto
Secret Party House of the Hill Giant Playboy – level 4-8, probably suitable for upper heroic or lower paragon – link is found at The Dungeon Dozen, which is also good for a read – Reviews: I couldn’t find any, but I like it
To Rob a Witch, The Possession, The Six-Thousand Steps, The Tower of Madness, The Missing of Cloud Bluff, Hive of the Giant Bees, Dreams in the Cloud Castle – various levels, the winners of Bryce Lynch’s Adventure Design Contest (which he reviews himself).
I threw this list together quite quickly, so let me know if there are any dead/incorrect links.
Edit: I ran across a decent 4e adventure which is publicly available from WotC which I wanted to add to the list. I consider this to be among the best of 4e: The Last Breaths of Ashenport.