Most of these sites are for sources for How-to Instructions on cool props.
Prop Master -- Paul is a great, local haunter. He's got some good how-to's. He's also kind enough to host the Rocky Mtn Haunters gathering, and also does a DVD collection of haunts. Great guy!
Monster List -- One of the most comprehensive lists of links to halloween projects.
Haunt Project -- Another good source of halloween projects.
Imagineering -- Where we got our Magic Mirror from.