Here are some of my favorites:
Breaking News English: a site that gives world news in levels.
English Page: easy to understand grammar help.
LearnEnglishFeelGood: grammar exercises and videos with questions to practice listening.
Youtube: Because you can practice listening effortlessly!
Common Czech Mistakes in English
From American Embassy website:
Materials for Learning English
USA information (published articles)
Developing English Writing Skills
Learn American English online (different levels)
