These are some of my favorite haunt related websites. I've chatted with several of the haunters and they're really great folks. Many other haunt sites can be found via the monster list and the haunt forum. Also check the other guy's link pages for more.

this site has info on how to do just about anything.

the friendliest forum I've ever been a part of. lots of info.

55-gallon drum turned cauldron stirring witch project + more.

Krough makes amazing sculptures...

This site was the inspiration for my scarecrow prop...

Brewster Yard Haunt
good info on building several nice props, see haunt 101.
Site with lots of info on using wiper motors + more.
Has a great section on lighting theory and corpsing.