http://www.truecrypt.org/docs/plausible-deniability
[Disclaimer: I claim no glory here, it's been around for years.]
Scenario:
The FBI kicks your door in, arrests you for an alleged "cyber crime," and confiscates your computer[s.]
Since "Enhanced Interrogation" has been tacitly approved by the current regime, and you have not yet divulged any useful information via verbal / psychological assaults, the goons move forward with "Enhanced Interrogation," AKA torture.
They want the password to your TrueCrypt protected hard drive!
What to do?
Solution:
Plausibly Deniable Encryption.
Basically, you place a "hidden volume" within the free space on an encrypted TrueCrypt volume. [Disk partition]
This hidden volume can contain a hidden OS where you do your dirty work, and keep potentially sensitive information.
Done right, you'll end up with a hidden operating system which is difficult to discern from the random data which fills the free space on encrypted TrueCrypt volumes.
Since this process is so involved, and potential mistakes so costly, I'll refer the reader to the TrueCrypt site for the actual tutorial:
http://www.truecrypt.org/docs/plausible-deniability
Since you've setup a hidden OS [or 2, or 3...] and your outermost TrueCrypt volume, the one hiding the hidden OS, only contains legal - yet sensitive - data, such as financial information, divulging the password for the outermost TrueCrypt volume should not place you in any more jeopardy.
Be careful if you use porn as your baited sensitive information, as sometimes porn actors are actually underage. You don't want to end up in prison for child pornography!
Result:
So you divulge the password to your outermost TrueCrypt volume containing completely legal and innocuous data, file a lawsuit against the government, settle out of court for an undisclosed amount, move to some tropical hideaway, meet the woman of your dreams and live free for the rest of your life. safe in the knowledge that your hidden data is still hidden.
Considerations:
No "hacking" with the outermost TrueCrypted OS! Don't be sloppy!
Don't write data to disk while using the outer TrueCrypt OS, you might overwrite your "hidden" OS.
Take all regular precautions regarding anonymity.
Etc.