For a few months, I have been using the language forum on wordreference.com. Since then, whenever I have a translation or a grammatical question, I go on the language forum, and it works really well. For example, I've asked a question on the use of There is and There are because I've heard one of my teacher use (many times) There is with plural-countable nouns (i.e. There is two players). According to what I've learned in the past, this use was incorrect, but my teacher was a native speaker so I doubted my knowledge. After a short discussion on the question with other members of the forum, I found out that, according to prescriptive grammar, she was wrong. However, these people told me that native speakers of English frequently do this mistake orally but rarely on paper. The best explanation I was given for the occurence of this error was "I think it's because it flows off the tongue easily". Indeed, second language learners are often more aware of what they say than native speakers, which is probably why I was shocked by that mistake whereas native speakers did not react.
That upper paragraph was simply an introduction to how forums can be used as an educational tool. The one I talked about is worldwide, which means that there is a good sample to go over the questions being asked. If someone does not tell the right thing, chances are that someone knowledgeable will correct the mistake. Plus, moderators make sure that discussions remain focussed.
During the last week, we have been asked (in my Computer Applications in ESL Teaching class) to post in Mark's forum in order to know how to use a forum and discuss the relevance of implementing its use in teaching. For my part, I believe the idea isn't that bad. Often, students are more aware of their difficulties than the teacher is; this is because they themselves had to get over the difficulties. Therefore, letting students answer to other students' questions on a forum is certainly a great idea.
Similarly to the case of students, some studies show that second language speakers are better language teachers than native speakers since those teachers too understand the difficulties of the language being learned. Definitely, learners are the one that should teach to other learners.