Carbon Copy Cloner is a simple, donation-ware utility for cloning entire drives, performing incremental backups, and scheduling ongoing backups. This app has a long track record as one of the most useful and reliable disk utilities available, and its interface and features (especially for scheduling) have only gotten better. Its also kept up with the Mac OS, adding support for HFS+ filesystem compression. Other recent updates have integrated support and documentation into the app better, speeded up recovery of files from damaged volumes, and ensured that Carbon Copy Cloner excludes the Time Machine database.
Carbon Copy Cloner makes it very easy to quickly clone a hard drive (i.e., duplicate every single file on the drive, even at the block level), or you can indicate which files and folders should be copied--and you can also direct it to only copy files that have changed since the last backup. Carbon Copy Cloner can help you schedule regular backups, too, according to any schedule you set, and it can also work with iPods and remote Macs. Carbon Copy Cloner may have a fairly narrow feature set (for example, you can't back up directly to optical disks), but it provides a lot of well-executed functionality at a low price.