Hal Helms has posted an interesting quiz to his site:

Are you OO Ready?

It is pretty darn humbling. Here are some things to keep in mind. For a few questions, he assumes ColdFusion, but I read it as Java. This really tripped me up on more than one question. Also, I'm not quite sure a stack/heap question makes sense for an OO test, but that's probably just sour grapes on my part. (I won't tell you my score, but I've seen football games with larger numbers!)

Be sure to scroll down when you get your results. I didn't notice it under his ad, but he goes through every question and explains the ones you get wrong. This is where the really valuable advice is.