Want to take part in these discussions? Sign in if you have an account, or apply for one below
some more from me 
http://hairfinder.com/hairstylescollections.htm - tons of hairstyles
http://www.artrenewal.org/asp/database/art.asp?aid=187 - tons of great masters works
great references thanks
http://www.tommyedwards.com/gal_portfolio.htm
I find this one handy, don't know anyone who hasn't heard of it
- http://www.characterdesigns.com/
This is a pretty nice site for refs 
http://www.mademan.com/chickipedia/
reference pictures
http://www.artmorgue.com/home.cfm
Awsum link Peter!! Been looking for a decent medieval source for a while.
Modern Costume/Fashion Design Refs
http://www.thesartorialist.blogspot.com/
For emergency colour refrence, general inpiration or just some cool stuff:
http://blog.flickr.net/en
also http://www.darkroastedblend.com/