WinDSPAM is a statistical spam filter for Windows servers and clients based on Jonathan Zdziarski's DSPAM. Features (will) include intergration with Microsoft Exchange Server 2000/2003 and support for a variety of back-end databases.
SPAM-Buster is a Java application for filtering SPAM based on statistical algorithms (currently Bayesian). The platform independant application can be used as graphical end-user client and additional service for mail server.