B1 In Search of the Unknown was the first D&D map I ever saw. I still love that adventure to this day. Mike Carr exploited an incredible number of design tricks in creating the levels that make up Quasqueton. I find those maps inspirational to this day. As good as they are, however, I have always longed for more.
Beyond B1, I find maps from the following TSR modules to be inspirational for various reasons: C1 The Hidden Shrine of Tamoachan, D2 Shrine of the Kuo-Toa, G1 Steading of the Hill Giant Chief, G2 The Glacial Rift of the Frost Giant Jarl, G3 Hall of the Fire Giant King, and S1 Tomb of Horrors. In addition to modules, I still look at the Dungeon Geomorphs from time to time. As a matter of fact, I stared long and hard at them prior to drawing the maps for Pied Piper Publishing's DUNGEON SETS. Those geomorphs are crazy hectic and illustrate a lot of the dungeon design mores of their time.
Judges Guild appeared on the scene around the same time I got into TSR. Now I was never a Wilderlands person, but I do fondly remember pouring over the maps from Tegel Manor. The mansion was tremendous, but it was the dungeons that really fueled my imagination… Although I thought that the dungeon levels were too few (still think that), I found them awesome to behold. The claustrophobic tunnels winding throughout Level 1 and the intricate arrangement of rooms and passages on Levels 3 and 4 are equally inspiring. I continue to love the hatching style that was employed on these maps.
The same style can be seen in the maps of Castle Blackmoor, re-rendered for inclusion in the First Fantasy Campaign from 1980. Dave Arneson's designs are interesting. In particular, Level 5 opened up the possibilities of really crazy big levels—something which I have only experimented with in private.
Also worthy of inclusion are the maps from the early Middle Earth releases from Iron Crown Enterprises. Released in the early 1980s, these maps have proven to be very inspirational to me. I'm not speaking of the amazing color wilderness maps by Pete Fenlon. While works of art, to be sure, it is the black & white maps by Terry K. Amthor that have left their mark upon me. In particular, maps from Angmar, The Court of Ardor, and Moria all deeply influenced me. Even today I detect his influence in my maps. You know what? I'd have it no other way!
Other maps that I have seen over the years include various levels from both Castles Greyhawk and El Raja Key, all drawn by RJK, as well as facsimiles of various maps by EGG from the ill-fated Castle Zagyg line. As someone who "grew up on modules" (for better or for worse), it has been extremely satisfying to see and be influenced by these old works. The reason being that they simply don't resemble modules in the slightest.
In closing, I have to give my final nod to Tékumel and its vast underworlds. What can I say of these? Amazingly huge, that's what. I've seen a part of the Jakallan Underworld and all I can say is that it is an impressive maze, punctuated throughout by strange chambers and richly evil temples. This place is incredibly detailed. Alas, I've never seen a key for this, and the details I do have remain sketchy at best, so I can only imagine the myriad horrors that dwell within this dim place. (Actually, not having the key makes this map fragment that much more cool!)