Bayes nets - Probably a useful tool, maybe? (tutorial by Joe Tullio)
BayesiaLab offers a complete set of Bayesian Networks learning
a.. a set of very effective unsupervised learning methods for association discovery,
b.. unsupervised learning methods for new concepts discovery (segmentation, clustering)
c.. and supervised learning methods that focus on a target variable (from classical Naive Bayes classifiers to an original Augmented Markov Blanket learning allowing a tremendous gain in time and readability). BayesiaLab also comes with an analysis toolbox that allows discovering very quickly the strength and the type of the probabilistic relations encoded by the learned bayesian networks.
Bill Hsu's Bayesian Networks Formats Convertor
Kevin Murphy's Bayes Net Toolbox 2.0 for Matlab 5
Fabio Cozman's JavaBayes
Learning Bayes nets from data (in Java, open source)
Russell Almond's Software for Manipulating Belief Networks
free Bayes Net software
MSBN: the evil empire's BN software package.
Netica - Commercial Bayesian network, influence diagram, and decision network software from Norsys, Inc.
Genie - Bayesian network modeling tool from the University of Pittsburgh
Noetica Systems, Inc, with link to Ergo(TM): Bayesian Network Editor and Solver
Hugin expert (implements BNs and influence diagrams)
Stochastic Planning Using Decision Diagrams
A paper about whether it's easy to predict the effects on planning of changing probabilities in a BN, with links to various Bayes nets suitable for SPUDD experimentation.
Russ Greiner's BN links Lots of links to summaries of software, books, applications, etc.
Sara Farmer's list of links
the Bayesian Knowledge Discovery Project of The Open University
Probabilistic Reasoning Group, Kansas State University