http://owl.english.purdue.edu/owl/
The Online Writing Lab (OWL) houses writing resources and instructional material. You will find information to assist with many writing projects.
http://www.copyblogger.com/commonly-misused-words/
The Inigo Montoya Guide to 27 Commonly Misused Words — Copyblogger
http://ezinearticles.com/?The-Top-10-Grammatical-And-Spelling-Errors-On-The-Web-And-In-The-Office&id=425244
The Top 10 Grammatical And Spelling Errors On The Web And In The Office
http://grammar.about.com/od/c/g/causeeffect.htm
cause and effect - definition and examples of cause and effect - development of paragraphs and essays