"Packet Scrubber" plug-in to Snort. This is the original posting about it on Security Focus that gives the whys, wherefors, and hows at a high-level.

SecurityFocus - HogWash

Interesting open letter from Dark Tangent (Jeff Moss) that reflects on DefCon's evolution and asks for feedback from the Hacker community on how to deal with some of the current issues.

A (sort of) Reflection on the Evolution of DefCon

Extremely good summer 2001 article on the state of IDSes

IDS Shootout