(note - I love this picture. It has thrown more that one player into a state of catatonic fear upon a mere viewing.)
I was not aware of this, but at some point, Wizards of the Coast was giving away old Dungeons & Dragons modules from the 1980's for free. Well, at least pdf copies. This giveaway appears to have happened around 2000 to 2002. I stumbled upon them today and was pleasantly surprised.
Of course this may be common knowledge and I'm the last on the boat. For those who haven't seen them, they lie deep in the bowels of the WotC site. There are four articles and (if I'm counting right) five modules:
B3. Palace of the Silver Princess
L2. The Assassin’s Knot
Ravenloft II: The House on Gryphon Hill
EX1-2. Dungeonland and The Land Beyond the Magic Mirror
So quick, sneak through the castle in the clouds and grab the goodies before the gruff giant wakes up, realizes what he's done, and locks them away.
Oh, and if you know of any more of these gems, please share the location.