I wrote a little article on the use of business rules in the context of agile methods to deliver true business agility for InfoQ recently - Agile Business Rules. Deborah Hartmann also wrote a nice introduction When and How to Formalize Business Rules. For those of you who have not discovered InfoQ yet I highly recommend it. Some nice technical articles grouped into some core topic areas with some (lightly) personalized feeds based on those topic areas. They already had another article about business rules by Geoffrey Wiseman "Real-World Rules Engines"