Wikipedia is a good source for general information in my opinion. You shouldn't use it for study purposes, but it will give you a good idea of many subjects.

It is all written by volunteers so there is plenty of room for human error, but I think that in general it is a good resource.

It's great fun if you want to post a piece of general information on a subject on a forum, there is always a really pedantic member who just waits, salivating, to correct the mistakes. That makes me laugh sometimes.

So, good for info, but you won't pass your exams using it. It does often provide links to more in-depth information though.