Touchgraph and Amazon
Alex Shapiro over at Touchgraph (proof that Open Source can be truly innovative!) has added an Amazon browser to the way-cool Google browser. For all you teenage girls out there, there's a LiveJournal browser as well. The Amazon implementation is based on 'customers who bought also bought' and the discussion includes a link to a good IEEE article on recommendation algorithms, including collaborative filtering, cluster algorithms, and search-based methods. The article serves as a handy collaborative filtering primer.