Here are some web sites and books that have been very helpful or inspiring to my work:
Web sites
The Wet Plate Collodion Photography Forum - http://www.collodion.com
Getting Started in Wet Plate Collodion Photography - http://unblinkingeye.com/Articles/WPC/wpc.html
John Coffer's web site - http://www.johncoffer.com
Scully & Osterman - https://www.collodion.org/tutorials-1
Early Photography - http://www.earlyphotography.co.uk/index.html
Books
John Coffer - The Doer's Guide to Wet-Plate Photography, 2000
Jill Enfield - Jill Enfield's Guide to Photographic Alternative Processes, 2013
Quinn Jacobson - Chemical Pictures: The Wet Plate Collodion Book, 2013
Christopher James - The Book of Alternative Photographic Processes, 3rd edition, 2015
Mark Osterman & France Scully Osterman - Basic Collodion Technique: Ambrotype & Tintype, Version 5, 2013
Barbara Upton & John Upton - Photography, 2nd edition, 1981