links
Here is a list of links that I have found helpful in costuming.

Costuming sites:
Alley Cat Scratch's LOTR Site
Padawan's Guide to Star Wars Prequel Costumes
Costumer's Guide
Chivalry Sports Renaissance Store
Web Gallery of Art (good for historical paintings to model costumes after)
Jedi Council Forums
A Festive Attyre
Elizabethan Costuming
SCA Garb Links
The Wardrobe Door, one of the best Narnia Costuming Sites
Demode has one of the best lists of links I've found