This page lists websites useful for ready reference on questions of vocabulary, syntax, grammar and mechanics.

Merriam-Webster's Online Dictionary

Roget's Interactive Thesaurus

Strunk's Elements of Style (the original version), and U. of Toronto's Developing Coherent Paragraphs.

Grammar and Mechanics at the Online Writing Lab (Purdue), and an annotated collection of grammar sites from the University of Chicago Writing Program.  See also The Internet Grammar of English at the University College, London and The Guide to Grammar and Writing at Capitol Community College, Hartford, CT.