In addition to APA, MLA, and Chicago styles, there are quite a few styles that different fields use. Below you will find some of the more common styles that are used with links to resources to help you with them.
Turabian (Kate L. Turabian) style is widely used in cite with in literature, history and the arts.
Links to a guide created by Monash University on the Harvard Style.
Guide to formatting and citation in the ASA (American Sociological Association) style from the Purdue Online Writing Lab
IEEE Editorial Style
Style Manual for Institute of Electrical and Electronics Engineers (IEEE)