If you want to try out a new Linux distro, be it the latest Ubuntu 11.04 Natty Narwhal daily ISO or any other (I've only tested it with Ubuntu though!) and don't want to burn a CD each time you want to try a new daily build (and you don't have an USB memory stick around), you can use a cool GRUB 2 feature that lets you boot a live CD ISO directly from your hard disk. You can also use this method to boot varous utilities such as Super Grub Disk, SystemRescueCD, Parted Magic and so on.