Editing Tools

American Copy Editors Society
AssignmentEditor.com (good editors' portal; but requires subscription)
Blogspot (lively blog for copy editors)
CJR's Language Corner
Rhymezone (rhymes, synonyms, definitions, and more)
Slang guide
Strunk's Elements of Style online (the copy editors' bible)
Troublesome words (searchable database for troublesome words)
Word Police (wordsmithing site by Atlantic magazine's editing maven)