One of my former students has just published an article that may interest my readers:
Leslie Porter: Library applications of business usability testing strategies
Library Hi Tech, Volume 25 Issue 1 (2007): pp. 126-135. (a subscription is required for access)
This is a great review of articles from the business & computer science literature on usability testing, suggesting what we in library-land can learn from those in other disciplines. I'm a little biased, but I think it's an important article.