Self organising maps (SOM) represent a particular use of neural network technology with the aim of visually displaying data clustering.
R – a package exists for R called kohonen which supports both supervised and unsupervised SOM.
Spice-SOM runs on Windows and is a stand-alone SOM utility with the feature that the distance between neurons can be displayed on the output map.
Tanagra – SOM are included in the data mining techniques used by this advanced data mining suite of tools.
Weka – includes SOM capability. It can be downloaded as a separate library if needed.