Here's a link to a rather tricky online grammar test.
Quiz - How grammatically correct are you? (Revised with answer.. - grammar - Quizilla Quizzes
It's a bit of fun (although I did it in front of a class and was sweating at some points, I can tell you!)
Have a go and see how you get on. Then check the answer key and see if you agree. There's one or two that I don't agree with and I'd be interested to hear what you guys think.
Have fun.