There are actually a couple of books that can probably help with this kind of informal user experience testing. Both are by Steve Krug. The first is "Don't Make

There are actually a couple of books that can probably help with this kind of informal user experience testing. Both are by Steve Krug. The first is "Don't Make Me Think" which focuses on design for usability, and includes a chapter titled "Usability Testing on 10 Cents a Day". The second is "Rocket Surgery Made Easy: The Do-It-Yourself Guide to Finding and Fixing Usability Problems" (already mentioned by petervandijck). This is a newer book (2009) that goes much more deeply into usability testing for people whose primary responsibility is design and development rather than user experience. It's a great book in spite of the cutesy name.