<p>As a second interview I get people to sit down and write code...I try to make the problem really technology independent.</p>

<p>My programming problems that I have don't really exercise peoples OO abilities.  I tend to try and keep the coding problem solvable within 2 hours ish.  So, I've struggled to find a problem small enough and involved enough that it exposes peoples OO design skills.</p>

<p>Any suggestions?</p>

These aren't specifically OO Questions, but check out the other questions tagged
interview-questions
Edit: What about implementing some
design patterns
? I don't have the best knowledge in the area but it seems as if you would be getting two questions for the price of one. You can test for both OO and Design pattens in the one question.