Info useful to playwrights:

Theatre Communications Group
American Theater Web
Playwriting Opps for the E-Merging Writer
The Dramatists Guild
The Playwrights' Noticeboard
International Centre for Women Playwrights
Literary Managers and Dramaturgs of the Americas
Curtain Rising
Playwrights Guild of Canada
Copyright Laws for Theatre People
What is Copyright Protection?
English-Language Playscripts at The Library of
NY Play Development
The Theater Cooperative of Los Angeles
Broadway Online
Off Broadway
Off-Off-Broadway Review
The World Wide Web Virtual Library Theatre and
UK Theatre Web
US Copyright Office
Mojo Theatre

Info useful to playwrights,
er/re fans, and other   
interested visitors:

Theatre History
Theatre Development Fund
Stage Direction Magazine
Theatre on a Shoestring
Glossary of Technical Theatre Terms
Society of Stage Directors and Choreographers
The Actors Studio
The London Academy of Music and Dramatic Art
Royal Academy of Dramatic Art
San Diego Theatre Scene
The Internet Theatre Bookshop