e-fense has released helix, i haven't tried it out yet but it seems useful for testing what information your computer is leaving behind

http://www.e-fense.com/helix/

"Helix is a customized distribution of Ubuntu Linux. Helix is more than just a bootable live CD. You can still boot into a customized Linux environment that includes customized linux kernels, excellent hardware detection and many applications dedicated to Incident Response and Forensics.

Helix has been modified very carefully to NOT touch the host computer in any way and it is forensically sound. Helix wil not auto mount swap space, or auto mount any attached devices. Helix also has a special live side for Incident Response and Forensics.

Helix focuses on Incident Response & Forensics tools. It is meant to be used by individuals who have a sound understanding of Incident Response and Forensic techniques."