The MatCompare software provides methods for comparing transcription factor binding site (TFBS) position frequency matrices (PFMs). The user has a choice of using the Kullback-Leibler divergence, the chi squared test or the Fisher-Irwin exact test of similarity.
A stand alone version of the software can be downloaded here
MatCompare can also be downloaded as part of the CREAD package.
Dustin E Schones, Pavel Sumazin and Michael Q Zhang
Similarity of position frequency matrices for transcription factor binding sites
Bioinformatics 2005 21(3):307-313; doi:10.1093/bioinformatics/bth480