SpamCannibal blocks spam at the origination server and can be configured to block DoS attacks.
see: https://spamcannibal.svn.sourceforge.net/svnroot/spamcannibal spamcannibal for svn repository or visit http://search.cpan.org/
Tarwrap is a wrapper program written in C which will allow users of LaBrea Tarpit to log tarpitting, activity and bandwidth to a MySQL database for easy use. This adds many features making LaBrea and Tarwrap a robust tarpit solution.
WASP: Wiredance Anti-Spam Project - Spambot poisoning for the whole family. Generates a page with fake email addresses for spambots to follow, and "tarpit" links so that they'd get stuck there and harvest their own addresses.