This comes from a publication from my alma mater, but I don't think that makes me any less impartial than I should be. I have been thinking about my courses for next year quite a bit lately, and I had already decided to incorporate some form of regular, low-stakes testing for a variety of reasons. This article is a nice confirmation of that decision.
People learn best when they are forced to retrieve the information and concepts repeatedly over time but most people haven't learned to study in ways that do this. Consequently, it may be more effective to move from the common practice of giving a few, high-stakes tests to giving numerous low stakes quizzes to assess and improve learning.