What is algorithm behind the recommendation sites like last.fm, grooveshark, pandora?

Question

I am thinking of starting a project which is based on recommandation system. I need to improve myself at this area which looks like a hot topic on the web side. Also wondering w

Answer 1

Great paper by Yehuda Koren (on the team that won the Netflix prize): The BellKor Solution to the Netflix Grand Prize (google "GrandPrize2009_BPC_BellKor.pdf").

Couple websites:

• Trustlet.org
• Collaborative Filtering tutorials by Dr. Jun Wang
  
• Google: item-based top-n recommendation algorithms