PolyAnalyst, offers clustering based on Localization of Anomalies (LA) algorithm.
StarProbe, cross-platform, very fast on big data, star schema support,
special tools & features for data with rich categorical dimensional information.
Visipoint, Self-Organizing Map clustering and visualization.
free:
Autoclass C, an unsupervised Bayesian classification system from NASA, available for Unix and Windows
CLUTO, provides a set of partitional clustering algorithms that treat
the clustering problem as an optimization process
Databionic ESOM Tools, a suite of programs for clustering, visualization, and classification with Emergent Self-Organizing Maps (ESOM).
MCLUST/EMCLUST, model-based cluster and discriminant analysis, including hierarchical clustering. In Fortran with interface to S-PLUS.
PermutMatrix, graphical software for clustering and seriation analysis, with several types of hierarchical cluster analysis and several methods to find an optimal reorganization of rows and columns.
PROXIMUS, a tool for compressing, clustering and discovering
patterns in discrete datasets.
Snob, MML (Minimum Message Length)-based program for clustering