I can think of a number of ways to fool the average Border Goon. Here's one which wouldn't be too tough for most Windows power-user types and a piece of cake for you Penguin-y types.

Just for "practice" sake you could create a second user account. In Windows at least, you can make sure that account is visible on the Welcome screen and your usual one isn't. I've heard rumors that Border agents type in the password and bring up your mail and browser. So obviously you'd want those to look "used". Maybe you could add in some files... a few pictures of unicorns and rainbows for them to look at.

To discourage identity theft the other account's sensitive data would be on a strongly encrypted partition that mounts onto the user's document (or home) directory. In XP you could accomplish this via the little known NT junction capability.

Have fun and stay free!