The Internet has become a tremendous source of information for actors and other show biz folk, visual artists, musicians and singers, and writers - these are some of the Websites I have found useful:

Actors, Directors, Dancers and Other Show Biz Folk
Visual Artists
Musicians & Singers
Writers

General Services Administration - Primary source for foreign & domestic per diem rates.

Internet Resources for Actors, Directors, Dancers and Other Show Biz Folk

Academy of Motion Picture Arts & Sciences
Actors' Equity Association
American Society of Composers, Authors & Publishers
Artmorpheus, Massachusetts-based non-profit for local artists and arts communities
Dance Magazine
Directors Guild of America
Filmmaker Magazine
Independent Feature Project
Independent Magazine for Magicians
Links to performing arts organizations
Manhattan Association of Cabarets & Clubs
Motion Picture Association of America
National Acadamy of Television Arts & Sciences
Playbill Magazine Online
Pointe Magazine, Ballet at its Best
SAG & AFTRA
Show Business Online
Stage Directions Magazine
The American Film Institute
The Great All Movie Guide on the Web
The Hollywood Reporter
The Internet Theatre Magazine of News and Reviews
The Musician’s and Performing Artists’ Guide to Successful Touring.  Agent Jeri Goldstein’s excellent site.
The US Government Copyright Office
TheatreBooks Online
Theater Resources Unlimited
Variety Magazine
Women’s Project.  Resource for women in theater
Tax Resources
The Internal Revenue Service
FCIC National Contact Center
The Single Best Source of Facts on the Internet
.

Internet Resources for Visual Artists

Art Access Website
ArtBusiness.Com
Art Business News
Art History Resources
Artmorpheus, Massachusetts-based non-profit for local artists and arts communities
ArtSource Website
Art Support.
Buy & sell stock photography – free membership
Dan Heller.com. A lot of info on the business of photography
Graphics Artist Guild
independent reviews of photographic equipment, extensive articles, tips & teaching
Home of "absolutearts.com"
News & Blog items on the business of street painting
New York Foundation for the Arts
Passion4art Website
Resource Library Magazine Listing of Art Museums
The Artchive
The Museums Website
The US Government Copyright Office
Tax Resources
The Internal Revenue Service
The Single Best Source of Facts on the Internet

Internet Resources for Musicians & Singers
Artmorpheus, Massachusetts-based non-profit for local artists and arts communities
American Federation of Musicians
American Songwriter Magazine
American Society of Composers, Authors & Publishers
Audio Engineering Society
Billboard Magazine
Bostons Premier Voice Studio - Jeanne Deva Voice Studio of Boston
Broadcast Music, Inc.
CMJ New Music Report Website
Copyright Society of USA
Film Music Magazine
Film Score Monthly
Just Plain Folks. Music community networking resource.
Live Sound International
Music Business Solutions
Musicians Contact Service. Connecting musicians & singers to paying gigs.
Music Publishers Association
Music Maker Publications Online
National Music Publishers Association
Professional Sound Magazine Online
Recording Industry Association of America
RecordLabelResource.com. Resource for starting/maintaining independent record labels.
Songstuff
The All Music Guide on the Web
The Concert Hotwire - touring info on the Web
The Dramatist's Guild
The Musician’s and Performing Artists’ Guide to Successful Touring. Agent Jeri Goldstein’s excellent site.
The Ultimate Band List on the Web
The US Government Copyright Office
Tax Resources
The Internal Revenue Service
The Single Best Source of Facts on the Internet

Internet Resources for Writers
Artmorpheus, Massachusetts-based non-profit for local artists and arts communities
Bookwire.com
Forwriters.com. Huge collection of links for writers.
The International Association of Media Tie-in Writers. For writers using existing movie, TV, book, game & cartoon characters.
National Writers Union
National Writing Project
PEN's official web site
Poets & Writers. The nation’s largest non-profit for creative writers; contests, grants, awards, job listings, etc.
Publishing Law Center
Right-Writing. Advice, links, articles compiled by agent/editor/writer W. T. Whalen.
The American Booksellers Association
The American Society of Composers, Authors, and Publishers
The American Society of Journalists and Authors
The Authors Guild
The Dramatists Guild
The Editorial Freelancers Association
The Small Publishers, Artists and Writers Network
The Society of Professional Journalists
The US Government Copyright Office
The Writer's Resource Center
ScriptFly - great source for links, particularly for screenwriters
The Writers Write Resource
Writers Digest
Writers Guild of America
Tax Resources
The Internal Revenue Service
FCIC National Contact Center
The Single Best Source of Facts on the Internet