We did this for our most recent hire - gave them a short project to implement over a long weekend. I think we shot for a target of having it take the applicant

We did this for our most recent hire - gave them a short project to implement over a long weekend. I think we shot for a target of having it take the applicants at most four hours; I threw together the reference example in an hour or two. I think it was a success, and we'll probably use this method going forward. There's just no substitute for seeing actual code, and by extension, the way someone structures the problem in their mind. It also give you some easy jumping off points to discuss with the applicant - Can you explain why you used data structure X here instead of Y? Change this requirement, and how would you do this differently? etc.