2 Books - highly recommended!

• Pierre Baldi et. al.; Modeling the Internet. Probabilistic Methods and Algorithms for the Web.


• Toby Segaran; Programming Collective Intelligence.

More than 220 Papers about Recommender Systems:

Davor ČubraniĆ, Gail C. Murphy, Janice Singer, and Kellogg S. Booth.
Learning from project history: a case study for software development.
In CSCW '04: Proceedings of the 2004 ACM conference on Computer supported cooperative work, pages 82--91, New York, NY, USA, 2004. ACM Press. [url].

E. Aïmeur, G. Brassard, J. M. Fernandez, and F. S. Mani Onana.
Privacy-preserving demographic filtering.
In SAC '06: Proceedings of the 2006 ACM symposium on Applied computing, pages 872--878, New York, NY, USA, 2006. ACM Press. [url].

Alfarez Abdul-Rahman and Stephen Hailes.
A distributed trust model.
In NSPW '97: Proceedings of the 1997 workshop on New security paradigms, pages 48--60, New York, NY, USA, 1997. ACM Press. [url].

Gediminas Adomavicius, Ramesh Sankaranarayanan, Shahana Sen, and Alexander Tuzhilin.
Incorporating contextual information in recommender systems using a multidimensional approach.
ACM Trans. Inf. Syst., 23(1):103--145, 2005. [url1]. [url2].

Gediminas Adomavicius and Alexander Tuzhilin.
Personalization technologies: a process-oriented perspective.
Commun. ACM, 48(10):83--90, 2005. [url] [url].