The New RefWorks (Version 3) offers a well-designed interface and many new features.
For specific style guides, choose one of the tabs at the top of this guide:
Humanities - (MLA, Chicago, Turabian, SBL, Notes)
Social Sciences - (APA, Chicago, Turabian, AAA, legal & government documents)
Sciences - (APA, ACS, AIP, AMA, CSE, GSA)
Images - works of art, photos, etc.
Audio & Video - music, film, etc.
Citing Sources (Duke University)
Includes instructions and examples for five major styles (MLA, Turabian, APA, Chicago, and CSE).
Citing Primary Sources - University of Wisconsin-Milwaukee Libraries
Citing Digitized Primary Sources - Teaching with Primary Resources Partners / Barat Education Resources
The Jacobson Center for Writing, Teaching and Learning offers individual help with writing and also this useful guide:
Writing Papers: A Handbook for Students at Smith College
Read "When to Cite" starting on page 47 (pg.54 of 71 in pdf file).