Style Manuals & Citation Guides

APA Formatting and Style Guide (Purdue University)

AP Stylebook AP does not offer institutional subscriptions, but individuals may subscribe to the online stylebook for a modest fee. 
See, too, the " Guide to AP Style."

NU only Chicago Manual of Style (Online)

NU only Elephants of style: a trunkload of tips on the big issues and gray areas of contemporary American English / Bill Walsh. 

NU only English for journalists / Wynford Hicks.

NU only Lapsing into a comma: a curmudgeon’s guide to the many things that can go wrong in print--and how to avoid them / Bill Walsh.

MLA Formatting and Style Guide  (Purdue University)

NU only New York Times manual of style and usage / Allan M. Siegal.  

Newsroom101:  An excellent site with over 1500 free exercises in grammar, usage, and Associated Press style. Created for journalists and journalism students.