"How To: Disable Your Passport's RFID Chip"

From Wired Magazine:

Passports issued by the US State Department after January 1 will have always-on radio frequency identification chips, making it easy for officials – and hackers – to grab your personal stats. Getting paranoid about strangers slurping up your identity? Here’s what you can do about it. But be careful – tampering with a passport is punishable by 25 years in prison. Not to mention the “special” customs search, with rubber gloves. Bon voyage!
1) RFID-tagged passports have a distinctive logo on the front cover; the chip is embedded in the back.
2) Sorry, “accidentally” leaving your passport in the jeans you just put in the washer won’t work. You’re more likely to ruin the passport itself than the chip.
3) Forget about nuking it in the microwave – the chip could burst into flames, leaving telltale scorch marks. Besides, have you ever smelled burnt passport?
4) The best approach? Hammer time. Hitting the chip with a blunt, hard object should disable it. A nonworking RFID doesn’t invalidate the passport, so you can still use it.
– Jenna Wortham