For the truly security conscience take a look at the IronKey USB drive....hardware military-grade encryption, tamperproof, self-erase after 10 bad password attempts, waterproof, etc. If you pick a good password / passphrase your data should be very secure.

They offer a way to backup all data using the same encryption so you can securely backup data on the device / media of your choice and later restore it to a new device if needed. (They also offer password/passphrase escrow - if you lose or forget your password your data cannot be recovered.)

It doesn't require special drivers or installation of any type. When you insert it, a ROM-based application to unlock the drive runs. Enter your password, the drive unlocks and you have access to the data as well as a few applications. For example, a version of Firefox that surfs the web using special Tor servers that Ironkey provides is built-in. All the applications run without having to be installed similar to the portable app suite.

http://www.ironkey.com