SuperDuper!

As a long time Mac user (since 1984) a have one really big complaint about MacOSX, and that is the incapability of the Finder to easily copy a bootable System folder to an external disk and boot from there. Enter SuperDuper!, a 20$ software for MacOS X, that allows you to copy entire disks, even in the unpaid version. The paid version has tons of additional features, but all with a really easy and understandable user interface. Highly recommended and compatible with MacOS X 10.4, too.