Zoterobib: Citation tool to build a bibliography for a paper in any citation style (APA, Chicago/Turabian, MLA)
Purdue's OWL (Online Writing Lab) APA Guide. NOTE: please skip the big green "Start Now" buttons on the Purdue site as they're only ads!
Knightcite is an online citation generator service provided by the Hekman Library of Calvin College; it's free but you register to use it.
Purdue's OWL (Online Writing Lab) Chicago Guide
Society of Biblical Literature (citing sacred text)
Purdue's OWL (Online Writing Lab) MLA Guide
Chicago/Turabian formats for music (songs, recordings, compositions, etc.) (Courtright Memorial Library, Otterbein University)