The Oracle Data Mining page on the Oracle Technology Network (OTN) provides a wealth of information, including white papers, demonstrations, blogs, discussion forums, and Oracle By Example tutorials:
http://www.oracle.com/pls/topic/lookup?ctx=db121&id=datmin
You can download Oracle Data Miner, the graphical user interface to Oracle Data Mining, from this site:
http://www.oracle.com/pls/topic/lookup?ctx=db121&id=datminGUI