If you're setting your adventure in Greyhawk, the Wilderlands, the Known World from Basic/Expert, etc. there are also sites dedicated to specific settings, at which folks will often comment about adventure design, too.
DF is probably your best one-stop-shopping site, although there is some excellent dungeon/wilderness design discussion over at Knights & Knaves, in the various "Adventure Notes" forums for OD&D and AD&D. The site is at
http://www.knights-n-knaves.com/phpbb/
Scott---
K&K as well as DF would be good links to add to the links section if they're not already there.