[COSTUMING SITES, HOW-TOs, AND TUTORIALS]
Alley Cat Scratch - Mix of different How To's, largely Lord Of The Rings
The Costumer's Guide - Maggie's awesome, check out her stuff!
Padawan's Guide - Maggie's Star Wars Costuming Site
Rebel Legion - Worldwide Star Wars Costuming Community... this one's for the good guys
The Fighting 501st - Worldwide Star Wars Costuming Community for stormtroopers, Sith Lords, and other baddies... you will never find a more wretched hive of scum and villiany
TheForce.net Costuming Boards - Another good discussion forum

[NOTIONS]
CorsetMaking.com
CorsetMakingSupplies.com - Boning, lacing tips, and tons more

[FABRICS]
Denver Fabrics
Dharma Trading Co. - White Fabrics and Dye
Silk Baron - Silk Dupioni in any color you can imagine!
Thai Silks - All kinds of silk fabric

[Embellishments]
Fire Mountain Gems - Beads! Ton's of 'em! And jewelry making supplies!

[BOOKS & RESEARCH SOURCES]
The Costumer's Manifesto - A huge jumble of historical research resources
Dover Publications - Research books on historical subjects
Web Gallery of Art - Paintings and Statues from 1101-1850. Excellent for researching Renaissance Era clothing

[OTHER]
Dyeable Shoe Store
Face Change - Carries Kryolan Body Paints

[WEB RESOURCES]
Statcounter.com - Free Hit Counter