The links below may serve as additional learning tools for the specified topics.
http://aispace.org/dTree/
http://www.decisiontrees.net/node/16
http://www2.cs.uregina.ca/%7Edbd/cs831/notes/itemsets/itemset_prog1.html
OLAP tutorial: http://pagesperso-orange.fr/bernard.lupin/english/example.htm
http://www.ailab.si/orange/
K MEANS: http://home.dei.polimi.it/matteucc/Clustering/tutorial_html/AppletKM.html
Hierarchical Clustering :http://home.dei.polimi.it/matteucc/Clustering/tutorial_html/AppletH.html
Clustering on Graphs:http://jung.sourceforge.net/applet/clusteringdemo.html
Comparison of Clustering Algorithms: http://webdocs.cs.ualberta.ca/%7Eyaling/Cluster/Applet/Code/Cluster.html