Overview of many companies:
http://www.lazylionbooks.com/identifyingfirsts.htm (Currently disconnected)

Alfred A. Knopf 

A. L. Burt Company 
http://sdrc.lib.uiowa.edu/lucile/publishers/burt/BURT.HTM 
http://newportvintagebooks.com/library/publishers/publishers_ae.htm

Appleton
http://newportvintagebooks.com/library/publishers/publishers_ae.htm

Bobbs-Merrill Company / Bowen-Merrill
http://en.wikipedia.org/wiki/Bobbs-Merrill_Company

Chatto & Windus
http://www.randomhouse.co.uk/about-us/about-us/companies/uk-companies-and-imprints/vintage-publishing/chatto-windus
http://www.wilkie-collins.info/publisher_cw.htm
http://en.wikipedia.org/wiki/Chatto_%26_Windus

Chautauqua Press: 
http://www.crackerjackcollectors.com/Jeffrey_Maxwell/alphachautauquan/index.html 

Cupples & Leon 

David McKay
http://en.wikipedia.org/wiki/David_McKay_Publications
http://www.jacketflap.com/david-mckay-co-publisher-1467

Doubleday 
http://newportvintagebooks.com/library/publishers/publishers_ae.htm

Easton Press:
http://reviews.ebay.com/List-of-Easton-Press-100-Greatest-Books-Ever-Written_W0QQugidZ10000000003437990; http://reviews.ebay.com/Tips-on-collecting-Franklin-Library-and-Easton-Press_W0QQugidZ10000000003637632

Franklin Library: 
http://reviews.ebay.com/Franklin-Library-books_W0QQugidZ10000000007233986; http://reviews.ebay.com/Tips-on-collecting-Franklin-Library-and-Easton-Press_W0QQugidZ10000000003637632

Grosset & Dunlap 
http://www.bookthink.com/0007/07repr.htm

Henry Altemus Company 
http://henryaltemus.com/; 
http://reviews.ebay.com/Henry-Altemus-dating-your-book_W0QQugidZ10000000000884443;http://reviews.ebay.com/Altemus-Description-Errors_W0QQugidZ10000000010787255

Houghton-Mifflin
http://newportvintagebooks.com/library/publishers/publishers_fj.htm

John W. Lovell Company
http://www.henryaltemus.com/TomBrown/publishers/jlovell.html

Lee & Shepard / Lothrop, Lee & Shepard:
http://bookofbibliomaven.blogspot.com/2009/06/lothrop-lee-and-shepard-dating-your.html 

Little Golden Books: 
http://reviews.ebay.com/Little-Golden-Book-Editions-Pricing-and-Numbering_W0QQugidZ10000000000010801;http://reviews.ebay.com/Little-Golden-Books-Collecting-History_W0QQugidZ10000000000853290 

Modern Library
http://reviews.ebay.com/Modern-Library-First-Edition-is-it-REALLY_W0QQugidZ10000000001753379 

Putnam
http://newportvintagebooks.com/library/publishers/publishers_kq.htm

Random House
http://www.randomhouse.com/about/history.html

Riverside Press / Riverside Publishing Company
http://www.riverpub.com/about/history.html

Saalfield


Scribner's
http://newportvintagebooks.com/library/publishers/publishers_rz.htm

Whitman

Victor-Appleton