Joseph, the Greyhawk Grognard, has released a free PDF that includes his vision of Level 2 of the legendary Castle Greyhawk. It's over 20 pages of material, including new monsters, magic items, hand-drawn maps, and descriptions of nearly 200 rooms -- quite an impressive piece of work!
Best of all in my opinion is the "bare bones" approach Joseph takes in detailing the level. The minimum of mechanics means that the module will easily work with any D&D-derived old school game. Likewise, the spartan descriptions enable each referee to make the place his own, which is exactly what a good module should do.
Good stuff. Keep up the excellent work, Joseph!