Blue Book of Grammar and Punctuation http://www.grammarbook.com - an easy-to-use reference guide and workbook also available as an on-line resource.

Craft of Scientific Writing, The http://fbox.vt.edu:10021/eng/mech/writing/csw.html - helps scientists and engineers improve their writing.

File...Don't Pile! For People Who Write http://www.grammarpatrol.com/FDP/ - explains how to create an orderly and easy-to-use filing system.

Get it. Write. http://www.getitwrite.com/ - 32-page handbook intended to give you a lifetime of confident writing skills 

Guidebook to Better Medical Writing http://www.medwriting.com/ - how-to book for writing medical journal articles.

How To Get Happily Published http://happilypublished.com/  - by Judith Appelbaum.

Nitty-Gritty Grammar http://www.grammarpatrol.com/ : A Not-So-Serious Guide to Clear Communication - lively language guide to help determine if your participles are dangling or your modifiers are misplaced.

Style Meister http://www.castlecommunications.com/   - publication style guide for a variety of custom formats.

Ultimate Book of Writing Contests http://www.ult-media.com/ - reference book of english-language writing contests and competitions. 

Wired Style http://www.hotwired.com/hardwired/wiredstyle/ - principles of English usage in the Digital Age.