BestCrypt is a system encryption tool for the Mac. It allows you to create encrypted "containers", where you can store files. These containers are password-protected and there are different encryption algorithms that you can choose to protect them. The available algorithms are: AES, TWOFISH, IDEA, GOST, DES, CAST, BLOWFISH, BLOWFISH-448, BLOWFISH-128 and 3DES. You can also assign each container a size and change the file system used. After you create a container, you can mount it, to do that you will need to type in your password. While a container is mounted, you can put files and folders in it, and read its contents. Once you un-mount it, all of its contents are secure again.
On the main window, you will see information about the currently select container. On the left pane, you will see a list of all the containers that you have created. From here, you can set the containers to mount on user logon or have them always opened for reading only, which isn't really secure if what you want to do is to hide data.
In short, BestCrypt works very well. It has tons of options and it lets you keep your data safe by using one of many very strong encryption ciphers.