Five things to consider when researching with the Internet (aka The CRAAP Test!)
If you cannot answer these questions satisfactorily, reconsider using the information as a source.
Websites for costume, clothing and fashion images
Costume Page - Costume images and history
Costumer's Manifesto - Great resource for costume history by period
Library of Congress: American Memory Collection digitized portion of the archives including documents and visuals
LIFE Photo Archives "Search millions of photographs from the LIFE photo archive, stretching from the 1750s to today via Google."
Internet Archive a digital archive of images, moving images, texts and music. Examples: Godey's Lady's Book of Color Fashion Plates & Greek Dress
Europeana Fashion Portal (currently under development) is searchable by keyword (limit by garment type, color). This site will eventually provide an archive for contemporary and historical European fashion.
Dance
Ballerina Gallery - Ballerina photo gallery
Dance Heritage Collection - dance collection to preserve America's dance
Stage Craft
TheatreCrafts - Useful links and practical information for all aspects of technical stagecraft, including an online glossary and links to effects, sound, lighting, props, and stage management
Theatron - 3D models of various stages
Theatre (General)
Cesar - Database contains information on all aspects of the French theatre between 1600 and 1800
Didaskalia - An electronic journal and resource dedicated to the study of ancient Greek and Roman drama in performance
Internet Broadway Database - The IBDB (Internet Broadway Database) archive is the official database for Broadway theatre information. IBDB provides records of productions from the beginnings of New York theatre until today.
Noh Plays - English translations of 13 Japanese Noh plays, including a glossary
Performing Arts Encyclopedia - Explore music, theater, and dance at the Library of Congress
Speech Accent Archive - Audio samples of various language backgrounds
Theatre History on the Web - Jack Wolcott's website of theatre history resources