Disk cloning or copying serves several purposes. It can be helpful for users who want to migrate to a larger hard drive for instance, or used for forensic or file recovery purposes as it is usually advised not to work with the original source. You find plenty of disk imaging tools on the Internet, some free, and many commercial.
OSFClone is currently offered as a free solution, which is likely to change after the current beta test. The program is offered as an ISO image that can be burned to CD or DVD, and as a version for removable storage devices like Flash storage.