TrueCrypt

One of my new favorite programs is TrueCrypt. It does on-the-fly encryption of disks or psuedo-disks. The interface is slick and easy to use, and it offers several respectably robust crypto algorithms. I have been looking for a good, open-source, on-the-fly encryption program ever since I started carrying a USB flash drive with me everywhere. The thought of losing my drive (with notes, passwords, etc.) on it makes me more than a little nervous. Not anymore. TrueCrypt also runs in "traveler mode", so it doesn't need to be installed on a computer to use it. From what I've seen, this is the best program in its class.