Grammar Help
This is part of Ruth Vilmi's Web World. She's a lecturer in the Language and Communication Centre at Helsinki University of Technology.

English Grammar on line
This grammar has been put on-line by Anthony Hughes. It's part of the Digital Education Network.

Guide to Grammar & Writing
It is maintained by Professor of English Charles Darling for English courses at Capital Community College, Hartford, Connecticut

A check for grammar & style
It is a grammar and style checker. The basic check is free, the deep check needs a subscription.

Englisch-Hilfen.de
This site provides a great variety of aspects when learning Englisch. Explanations are in German.

ESL Cafe's Help Center
You can receive help from ESL/EFL teachers from around the world 24 hours a day, 7 days a week (Grammar, Writing, Vocabulary, Idioms, Slang, TOEFL).

English Plus+
Lots of grammatical help (punctuation, style, mistakes, etc.) There's also a spelling and grammar checker available.