5 links
2Neat Books
oodenski.com
Specializes in USGS professional papers, offprints of scientific publications and magazines.
Double Decker Press
doubledeckerpress.com
Road guides to National Parks in the western U.S. and Hawaii.
Sapsucker Books
sover.net
Catalog of used, out-of-print, hard-to-find, and selected new natural history books.