I have listed some of my favorite links to organizations, theatres, and production companies.
Each of the links will open in a new page.

Organizations

Actors' Equity (AEA)
www.actorsequity.org/home.html

American Guild of Musical Artists (AGMA)
www.musicalartists.org/

American Federation of Television and Radio Artists (AFTRA)
www.aftra.org/aftra/aftra.htm

American Guild of Variety Artists (AGVA)
http://americanguildofvarietyartistsagva.visualnet.com/

Directors' Guild of America (DGA)
www.dga.org/

International Alliance of Theatrical Stage Employees (IATSE)
www.iatse-intl.org/

Screen Actors' Guild (SAG)
www.sag.org/

Stage Managers' Association
www.stagemanagers.org/

Stage Management Network
www.smnetwork.org/

Theatre/Production Companies

Actors' Summit Theatre
www.actorssummit.org/

Cornerstone Theater Company
http://www.cornerstonetheater.org/

Opera Pacific
www.operapacific.org/

South Coast Repertory
www.scr.org/

Weathervane Community Playhouse
www.weathervaneplayhouse.com/

Personal Interest Links

Diamond Mountain
www.diamondmtn.org/

Free Hugs
http://www.free-hugs.com/welcome.shtml

Internet Broadway Database
www.ibdb.com

Internet Movie Database
www.imdb.com

Kitten War
www.kittenwar.com

Kitty Kind
www.kittykind.org

Madcap Haven
www.madcaphaven.com

Mighty Mutts
http://members.tripod.com/~MightyMutts/start.html

Pet Pro Life
www.petprolife.org

Stringberg and Helium
www.strindbergandhelium.com

We Are What We Do
http://www.wearewhatwedo.org/index.php