Sally C. Luscomb, The Collector's Encyclopedia of Buttons. (I've found this to be of limited use. It is aimed more towards collectors but does have some useful information.)
Hinks, Stephen. "A Structural and Functional Analysis of Eighteenth Century Buttons." Volumes in Historical Archaeology 32 (1988). (A decent resource. One which I have used many times.)
I should have a few more references floating around and will send them if I can get my hands on em. I will follow this thread with interest!
Bernie Slaughter
Project Director
HAA, Inc.