My original question and accepted solution was posted here: http://stackoverflow.com/questions/2483640/rails-association-question. Check that out first.
My follow-up question is this:
I want to return an object that has both the user attributes and the race attributes. That way I can access, for example, the user's name and the fastest_time. How can this be accomplished? I've tried several approaches, but none I've been satisfied with.