WotC has put the complete S series illustration booklets online as free downloads!
Dungeons of Dread is the reprint of the classic S series modules (S1 - S4). This is a nicely put together package of some killer modules, that I never had the good luck of actually playing all the way through.
If you are a fan of the printed word like I am you will have a real problem ripping out pages from the modules/reprint. WotC has resolved this dilemma by putting all four illustration booklets online for a free download. They look pretty good.
What makes this even better for all the DMs/gamers out there is that you don't actually need to own any of the originals (or even the reprint compilation) to use them. Grab these downloads and use them to set up the scenes for some adventures of your own devising. Why let iconic D&D art like this go to waste?