Brief Guide to Citing Government Publications - A well organized site by the Government Publications Department of the Regional Depository Library at the University of Memphis (TN).
Citing Electronic Information in History - An extremely large, comprehensive site with huge amounts of textual background. Good bibliography.
CSE Citation Style from the University of Wisconsin-Madison Writing Center. Scientific Style and Format: the CSE Manual for Authors, Editors, and Publishers, 7th ed. Council of Science Editors, 2006. [Index and Table of Contents are available at the CSE Website]
A Guide to Citing Maps - from Ohio Wesleyan University
ACS Style Guide -- from University of Wisconsin, Madison