Schneier has written about this before, and provided a protocol for a way to prevent search without having to lie to security agents.
Companies and individuals have dealt with this problem in several ways, from keeping sensitive data off laptops traveling internationally, to storing the data -- encrypted, of course -- on websites and then downloading it at the destination. I have never liked either solution. I do a lot of work on the road, and need to carry all sorts of data with me all the time. It's a lot of data, and downloading it can take a long time. Also, I like to work on long international flights.
There's another solution, one that works with whole-disk encryption products like PGP Disk (I'm on PGP's advisory board), TrueCrypt, and BitLocker: Encrypt the data to a key you don't know.
(the article goes on to describe exactly how you can use a key that you don't know)
http://www.schneier.com/blog/archives/2009/07/laptop_securit...
