Artist-recommendations is a project mainly written in JavaScript, it's free.
Simple script for producing some artist recommendations from Last.fm
Generates a list of artists you should checkout based on what your friends have been listening to.
Rename config.js.example to config.js and enter the correct api_key.
node artist-recommendations.js [name] where name is the username of the Last.fm user to generate recommendations for.
The script aggregates the top artists of the user's friends from the last 3 months. It then picks the first 10 (ordered by total number of plays) that the user has never listened to.