Astonishing Swordsmen & Sorcerers of Hyperborea for some time now.
+Eric Fabiaschi over at "Swords & Stitchery - Old Time Sewing & Table Top Rpg Blog" has been doing a great set of Retro-Reviews of what I have been dubbing my "Second Campaign"
N1 Against the Cult of the Reptile God
U1 Sinister Secret of Saltmarsh
U2 Danger At Dunwater
U3 The Final Enemy
C1 The Hidden Shrine of Tamoachan
Now I just need some adventures for levels 7-12/13 (I like the idea of going to 13).
Originally I had a bunch of desert themed adventures, but they really never felt right to me to be honest. Maybe I should be looking towards some of the newer OSR adventures like The Islands of Purple-Haunted Putrescence to fill out the other levels.
I like the idea of some stygian cult. Something that was a cross between Lovecraft, Howard and Clark Ashton Smith. I think it might be fun if this cult was a Demogorgon cult too, just because.
He also reviewed some adventures I have already run or used under different systems.
B1 In Search of the Unknown
B3 Palace of the Silver Princess
B4 The Lost City
X1 Ilse of Dread
X2 Castle Amber
S4 The Lost Caverns of Tsojcanth
If you get a chance, stop by his blog and read the reviews.
Edited to Add: U3