Books We Like (BWL) is the result of a smart idea to combine the latest trend of "tagging" with Amazon's Web Services. From
Librarystuff (via del.icio.us):
Use this site to discover books that others love, to recommend your own favorites, and to keep a reading list of books you want to remember. Use it to buy books through Amazon, Powells, etc. and contribute the commission to fund independent media. The system uses your existing accounts at those sites. Use it to psychoanalyze other users based on what books they like.
How is the site funded? Well, BWL is an Amazon Associate, so all purchases in an Amazon (or other) session that starts from BWL (by clicking on a book title for instance) are credited to BWL (usually Amazon Associates receive ~5% revenue of each purchase).