Theatre Communications Group - Organization for non-profit theatre in America.
Theatre Library Association - Also includes a nice selection of links under "Related Theater Resources".
American Theater Web - links to regional theaters nationwide
Backstage.com - look here for jobs!
Facets - Multimedia distributor.
Internet Movie Database - Phenomenal database of just about everything you would ever need to know about any film ever produced.
Internet Broadway Database - Format based on the Internet Movie Database, details of Broadway productions.
Obie Awards - Off-Broadway awards from The Village Voice.