Grammar & Style

• The Elements of Style by William Strunk, Jr.
  "This book is intended for use in English courses in which the practice of composition is combined with the study of literature. It aims to give in brief space the principal requirements of plain English style. It aims to lighten the task of instructor and student by concentrating attention (in Chapters II and III) on a few essentials, the rules of usage and principles of composition most commonly violated."
• Grammar, Punctuation, and Spelling Handouts from Purdue University's Online Writing Lab.
  This site is an excellent starting point if you need to brush up on grammar and punctuation basics.
• Style Manuals & Writing Guides
  APA, ASA, MLA, Chicago, and more.
• The Write Place
  The catalogue page for the Literacy Online Education (LEO) web site.
• The American Heritage Book of English Usage
  With a detailed look at grammar, style, diction, word formation, gender, social groups and scientific forms, this reference work is ideal for students, writers, academicians and anybody concerned about proper writing style.