Truecrypt is awesome, great performance (especially if it can use your hardware is compatible with its optimization) and free. Really easy to use and supports come cool features like a hidden operating system (for if you get held and gun point and asked for your password)
You can also configure Truecrypt to work with multiboot - so if you have Ubuntu, Chromium OS and Windows 7 for example it will still work
You can also configure Truecrypt to work with multiboot - so if you have Ubuntu, Chromium OS and Windows 7 for example it will still work