Some guys from Princeton found a way to defeat disk encryption systems by extracting the key from the memory of a computer/laptop. While this is not really new (other people did that before), their way is quite cool. They remove the RAM module from the computer and read it in a other computer in order to do this without loosing the content of the RAM module they freeze the RAM module and with freeze they really mean freeze.
Check out the demo video.
Their paper explains it in all details. Read it if you use disk encryption and feel safe.
 Cold Boot Attacks on Encryption Keys (paper, video, faq, ...)