UPDATE - 20170327 - Truecrypt was disconnected in 2014.ev when Microsoft stopped supporting Windows XP. DO NOT USE IT. This blog post must be considered historical in nature.
If you've been following the news media for the past year or so, stores have been cropping up with frightening regularity about travelers who are detained at the border while customs agents demand the login credentials for their notebook computers so that they can be examined for gods-know-what kind of information. From time to time, the hard drives of computers are actually imaged for later analysis. As if that weren't enough, the United States Supreme Court has stated the opinion that this is permissible and a legally defensible thing to do, regardless of whether or not you are an American citizens, regardless of whether or not you're actually up to no good. Just a few days ago, it came out that Canada is trying to push through the Anti-Counterfeiting Trade Agreement, which would make it legal for Canadian border authorities to search not only portable computers, but USB keys, cellular phones, and MP3 players for information (specifically, pirated MP3 files)... the very act of searching one's personal and corporate storage media constitutes a potential information spillage situation because it may not be possible to prove in a court of law that data wasn't copied during the search. You can't necessarily prove a negative when you're dealing with file systems.