Costume Research

AlleyCatScratch Great Lord of the Rings character breakdowns and now King Kong research
Padawan's Guide The best site for the Star Wars prequels
The Costumer's Guide Sister site for Padawan's Guide -- lots of incredible reference images for numerous films
Aranel Online Research for several movies, including Tristan + Isolde and Penelope
Jedi Council Forums Discussion pages for most Star Wars costumes
Serenifly Costumes Costume pages for most Serenity and Firefly characters
The Wardrobe Door Costume site for the recent Narnia movies
Naergi's Costume Site Includes Riddick costumes, Shakespeare in Love, Sleepy Hollow, and others

My Image Collections (on Photobucket)

Kingdom of Heaven
The Fountain: Queen Isabel
Alias: Sydney's Pilot Episode Disguise

Fabric and Supplies

Dharma Trading large supply of dyes and dyeable fabrics
Fabric.com good supply of dupioni and other fun fabrics
SyFabrics basics, but cheap, and great silk velvets
Thai Silks lots of fun silks, watch for specials
Denver Fabrics now Fashion Fabrics Club, silks and fun fashion fabrics, not the fastest customer service
Waetcher's Silk Shop a little pricey, but nice wools
Silk Baron fabulous silk dupioni colors
Trim Fabric great fabrics, lots of good trimmings
CorsetMaking.com everything you need to build a corset
Cosplay's Shop formerly CosWorx, great wigs, they also stock make-up, shoes, and other accessories
We Love Colors tights and stockings in lots of color and size options (including plus sizes)