Common Errors in English
A collection of common errors in English, with detailed explanations and descriptions of each error.

AskOxford: Better Writing
A very useful reference for classic errors and helpful hints with a terrible site navigation.

Dr. Grammar’s Frequently Asked Questions
Answers to common grammar questions related to English grammar, with examples and additional explanations.

English Grammar FAQ
A list of common English language problems and how to solve them. This list was compiled through an extensive archive of postings to alt.usage.english by John Lawler, Linguistics, U. Michigan, Ann Arbor.