TrueCrypt is a well known and trusted open source application for encryption. It allows you to create and manage an encrypted volumes that can be used seamlessly and transparently.
TrueCrypt on Ubuntu isn’t new, I have written about it before. The new TrueCrypt 5 includes a GTK graphical user interface for Linux users, system partition encryption with pre-boot authentication, and improved performance.
Installing TrueCrypt 5 in Ubuntu is easy: