SuperDuper! is famous for being one of the best backup solutions for years now on a mac. Until today, ironically Super Tuesday, there hasn’t been a version updated for Leopard. The new version 2.5 is out and it can perform side-by-side backups with Time Machine.
What does this mean? Well you can have a fully functional, bootable backup on the same drive that your Time Machine backup is performed. This is great for people with large 500gb, 750gb, and 1tb drives that are being used as a Time Machine Drive. Granted you will sacrifice space for Time Machine, but having a bootable backup can be priceless in a time of need.
It is a free program, but some of the advanced features like scheduling run you $28, which is well worth it.