Oh, my favorite...here's a great grammar, punctuation, and vocabulary test. Think you know the English language well? Test yourself. Here are my results:
You did so extremely well, even I can't find a word to describe your excellence! You have the uncommon intelligence necessary to understand things that most people don't. You have an extensive vocabulary, and you're not afraid to use it properly! Way to go!
Now I have to go look at the answer key and figure out which one(s) I screwed up!