OpenFPC
Full Packet Capture: Open Source and on your own commodity hardware.
OpenFPC is a set of scripts that combine to provide a lightweight full-packet network traffic recorder & buffering tool. Its design goal is to allow non-expert users to deploy a distributed network traffic recorder on COTS hardware while integrating into existing alert and log tools.
Looking for documentation?
Note that all documentation is work in progress...
For more information check out www.openfpc.org