The RFID Guardian project has released the hardware and software schematics for the latest version of its personal RFID firewall. The RFID Guardian is a device that detects all the RFID tags on your person (passport, transit pass, bank-card, toll-card, car keys, etc), and interdicts them so that they can't answer queries anymore. The Guardian can clone all of these tags, and emit their signal on demand, but unlike a dumb tag, the Guardian only emits when you tell it to, and gives you a central way to set and enforce policy about when you will be identified and by whom.
The new version is completely open, and the relaunched RFID Guardian site includes a wiki, source code repository and bug-tracker. Link (Thanks, Melanie!)