Bart Goethals provides implementations of several well known algorithms including Apriori, DIC, Eclata and Fp-growth.
FPM contains all the C modules for various frequent item set mining techniques, along with an association rules GUI and viewer.
FrIDA – A Free Intelligent Data Analysis Toolbox
This is a Java-based GUI to data analysis programs written by Christian Borgelt in C. It includes basic visualization capabilities (scatter plots, bar charts etc) and visualization modules for decision and regression trees, and prototype based classifiers. Modules are also included for naive and full Bayes classifiers, radial basis function neural networks, multilayer perceptrons, multivariate and polynomial regression and association rule induction.
A pdf describing FrIDA can be found here.
KNIME – provides basic association rules mining capability.
Magnum Opus is an association discovery tool that majors on the qualification of associations so that trivial and spurious rules are discarded, based on the measures the user specifies. The tool is easy to use, fast (linear relationship between compute time and data size) and is available in a free demo version throttled to 1000 cases.
Rapid-i – includes several algorithms as part of it’s broad data mining capability.