A good resource on Data Mining using R environment is “Data Mining – Desktop Survival Guide” by Graham Williams. Its a well researched and frequently updated free online book. Graham does a good job of going through the data mining process and provides detailed descriptions of the commonly used algorithms.

Exmaples are in R (all with R source code, of course), with some good examples of graphical visualization as well.

Click here for Data Mining – Desktop Survival Guide

R Environment is a part of DecisionStudio-Professional and can also be separately downloaded from http://r-project.org.