Really good disk encryption and much more: Truecrypt 5

I have been a long time user of Truecrypt and have used it to protect personal and business documents on hard disks and even more on USB dongles (with what is called virtual encrypted disk).
Recently the TrueCrypt foundation released version 5 of their software which includes at least a couple of great new features, entire partition with pre-boot authentication and storage device encryption.
Another really cool feature for what they call "plausible deniability", which essentially allows you to have two passwords, one that gives access to your files and a second to use in case someone forces you to reveal it, in which case you are granted access to a set of valueless files you have previously saved.

The most recent release, 5.1a has also solved the problems related to hibernation, which was previously blocked when full disk encryption was activated (not so great for laptops).

I have encrypted my laptop's system disk and one great side-effect is a visible improvement in disk performances, evidently the new disk access drivers implemented have been so well optimized that they outperform Microsoft's native drivers even while adding the encryption layer.