EnglishLearner.Com
Learners of English will find all types of interactive tests and exercises here: Grammar, vocabulary, reading, crosswords, hangman and more. EnglishLearner.com also offers English lessons by e-mail at three levels every week - completely free.

Englisch-Hilfen.de
They provide a great variety of aspects when learning Englisch, especially grammar and vocabulary. Explanations are in German.

English Club
They offer a great variaty of learning and teaching recourses.

English Language Practice Pages
Here you will find English language exercises written by a number of published English language specialists and contributing teachers. It's part of the Digital Education Network.

www.vocabulix.com
You will find a broad range of vocabulary, tests and exercises for three languages: English, Spanish and German.

www.owad.de
A nice idea to extend you vocabulary and phrasal knowledge. You can learn English with Paul Smith's One-Word-A-Day.

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

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).

eflweb
They offer a number of EFL and ESL related services, which will be of use to anyone whether they are students, teachers or schools. These include teacher recruitment and resourses, a shop full of EFL products, notice boards, courses for learners of all standards and a comprehensive directory of schools.

Language 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.

CNN Newsroom and Worldview for ESL
They offer grammar and vocabulary exercises.

www.languagegames.org
Nice site overview of language games from various countries.