I can give you an invite to Quora. Just leave a message with your email in the comments. Go here, or simply enter you email below:
I used to think that Quora invite is hard to get, because I have never been invited by anyone. I was wrong. A Quora account can invite as many friends. So I think I never got an invite is just because it is not popular enough. Ah, I got mine because I asked, and I was easily given.
In my opinion, I would say Quora is a great question-and-answer web service. I find it useful for asking good questions. If you have an account, please follow me :)