We usually have a take home quiz/test, it usually takes one hour or so to complete, and gives us a shot at seeing how one approaches certain problems. I once had a guy that built a whole web based suite that acted like a tour, took us through each problem and then ran the code and spit out the result and also showed the code running in the test in a syntax highlighted view. WAY over the top and took way longer then an hour, we hired him though :)