Green Lion Press A small independant book publisher specializing in history of mathematics and history of science. Includes information on ordering, books available, and how to contact them.
http://www.greenlion.com/
History of Science Society Dedicated to fostering interest and scholarly research in the history of science and its social and cultural relations. Site informs about the profession, teaching and research efforts, and society activities.
http://www.hssonline.org/
Horus Publications There is a lot of useful material for researchers in the History of Science (both beginners and the more experienced) here, but you will have to dig a bit through the site. From Professor Ronald Tobey of the University of California, Riverside.
http://www.horuspublications.com/index.html