Disk Inventory X
If you've ever wondered where all of your hard disk space has gone, Disk Inventory X is a great little application to show you where that missing space ran off to. With Disk Inventory X you can see graphically how your files are using your hard disk space. It's a great way to clean up large unused files.
But be WARNED again, DO NOT delete anything the private folder. The biggest file in there is your sleepimage which is used to write what is in the RAM to the hard drive when you put your Mac to sleep.
SuperDuper!
I've saved the best utility for last. SuperDuper! is perhaps the best backup and cloning utility for OS X. Although SuperDuper! is not free, it is quite cheap it only costs $27.95. And that price is worth it. The tech support for SuperDuper! is not short of world class. There is also a free version available but some of the best features are disabled.
Quick DMG
With this small tool, you can quickly create DMG archives. Select from any Finder zone or just drag-and-drop files/folders onto Quick DMG icon (place it in the Dock - Useful!). Simply follow a few dialog boxes. Compression method chooser for new DMG file is available in progress.