Most of you will have heard of Truecrypt, a free an open source hard disk encryption product, there are only another free and open source software for full disk encryption in Windows that I am aware of, DiskCryptor. You can download a 32bit or 64bit version of Diskcryptor depending on your OS.
I tested DiskCryptor using it for full disk encryption of my netbook, an Asus PC901 with a 12GB HDD divided in between two solid state disks of 8GB and 4GB. DiskCryptor is an ideal alternative to encrypt a netbook because netbooks do not have a CD drive and Truecrypt will force you to burn a CD to use system encryption, which DiskCryptor does not.
The first thing that impressed me of DiskCryptor is how small it is in size, a little over 500KB, but this comes at a price since the software manual does not come along and you get a link to their website instead.
I was pleased to see DiskCryptor offering a wide choice of encryption algorythms, AES-256, Twofish or Serpent algorithms in XTS mode, all of them seem to be pretty sound algorythms to me, and they can be used on cascade mode as well, VIA Padlock hardware accelaration for encryption and hashing is supported too.
The built-in benchmark shows the top speed with which cryptographic algorithms can perform, but I have to tell you that even on a netbook with a single core Intel Atom processor, regardless of the encryption algortyhm used I noticed no perfomance difference while using the netbook.
DiskCryptor allows wipe while encrypting, with three, seven or thirty five passes (Guttman method), but wiping a solid state disk like the one Asus Eee PC901 has is not safe, since solid state disks, like thumb drives, use wear levelling technology and the wiping passes are spread evenly accross the disk and not on the same sectors. If you are using a solid state disk, make sure it does not contain any confidential data that an electrons microscope could recover(very expensive to do right now), the only way to do this is by using a new disk, wiping it may fail to sanitize de disk.
With DiskCryptor you also can encrypt an ISO file and then burn it to CD-R/DVD/BD-R , after that you will only be able to mount the image with DiskCryptor and the correct password/keyfile.
You can also set up a hot key to cause a blue screen of death, if you need to urgently shut down your computer when someone busts into your home unexpectedly this seems the way to go, it is quicker than clicking on the power off button.
The Good Stuff
DiskCryptor works with RAID volumes, you get a wide choice of algorythms, DiskCryptor is easy to use and unlike Truecrypt, it works on netbooks out of the box. DiskCryptor is open source, you can check for backdoors if you have the skills.
The software does not cost you any money, you can customize the boot loader widely, DiskCryptor boot loader customization is far better than Truecrypt, you can choose to install the bootloader on a CD/DVD, set up timeouts, choose if you want to use a QUERTY or DVORAK keyboard, and there is also a Windows live CD BartPE plugin for DiskCryptor.
The Bad Stuff
DiskCryptor should include some basic documentation at the very least, the GUI is easy to use and intuitive but encryption products need to come with instructions, a newbie could easily feel overwhelmed. DiskCriptor is only available for Windows, and there is no choice of hashing algorythms other than the default SHA-512.
There is also no choice of burning a recovery CD in case the boot loader gets corrupted (although you can backup the headers).
DiskCryptor is an excellent free and open source full disk encryption alternative to Truecrypt, with a wide choice of encryption algorythms and easy to use, but they need to improve their poor documentation.
Their FAQ states that they are planning to implement a hidden OS in future versions, I think Diskcryptor looks promising and Truecrypt has a worthy competitor.