Serenifly Costumes covers the costumes worn on the show and does it very well. Here is a little about the owner, Mia.
Mia has been a fan of Firefly and Serenity since July 22, 2006, when she saw Serenity for the first time. Since then, she has made 7 Firefly-related costumes for herself and friends. She became interested in cataloging the costumes when she noticed Inara wearing something she’d already worn in another episode. That led to a number of screencaps and picture hoarding until she couldn’t keep track of it anymore. She finally started organizing and realized that having it online would make it easier for her to search for a costume. And, so it began.
Go visit at http://serenifly.blogspot.com/