Got files you need to protect from others? TrueCrypt is a great piece of software and it's completely free! It's very easy to setup, but if you need help with it the people on their forums are fantastic. Another piece of software I use, which I'll leave nameless, I asked for help on their forums and the people were snotty and a lot of times did not answer. The few times I've asked questions in refernece to setting up and using TrueCrypt for the first time, the forum people were quick to reply and helpful.
I am unsure of every feature TrueCrypt has, but I'll tell you what I like about it and what I use it for.
Let's say you have a computer with a bunch of free space on the hard drive. Let's say you want to store files and not risk others seeing them or even having access to them. You could be storing business files, bank information, or heck hiding porn from our old lady. You can basically make a TrueCrypt Container. This will show up in My Computer looking like another hard drive. It's password protected so only the person with the password can get in. It's strongly encrypted so not just anyone can hack it either.
What you do is create a container. It acts just like a hard drive would. You can copy files, delete files, make folders, and do other operations as you normally would. You first create the container by telling TrueCrypt how much space you want to make it (such as 1GB in size) and format it. Formatting might take awhile depending on your computer processor and memory. You can store this file anywhere on your computer. I'm sure people can still delete this file, but at least they can't access and see what's inside. Once your container is created, you need to mount it in order to use it. This is as easy as firing up TrueCrypt, selecting your container, entering your password, and hitting mount. You can mount it to any drive letter you want. When you're done using the container, go back into TrueCrypt and dismount the drive.