benefits of object oriented programming
http://www.devdaily.com/java/java_oo/node5.shtml
http://www.rtis.com/nat/user/jfullerton/BENEFIT.HTM
http://wiki.answers.com/Q/Benefits_of_object_oriented_programming
http://www.westga.edu/~bquest/1997/object.html
http://dotnetperls.com/Content/Object-Oriented-Benefits.aspx
http://www.stanford.edu/~pgbovine/programming-with-rep-invariants.htm
http://www.oei-edu.com/s656.htm
http://www.alagad.com/go/blog-entry/what-does-object-oriented-programming-do-for-me
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.2.8789
http://www.icsi.berkeley.edu/~sather/Publications/article.html
http://www.rbgrn.net/blog/2007/10/object-oriented-programming-explained-part-1-the-basics.html
http://journals.ecs.soton.ac.uk/java/tutorial/java/objects/index.html
Object Oriented PHP
Modularity
Implementation should be separate from the interface. Opting to not allow foreign code to access your internals buys you privacy and freedom to change around your internals.
