The next version of Ubuntu, "Dapper Drake", has an installer built into their LiveCD.
For those unaware, a LiveCD is a regular cd which, when in the cd drive when you boot your computer, boots into an operating system on the cd, rather than the one on your hard drive. This lets you try an operating system without risking your regular system.
Many Linux distributions have LiveCDs, and a few even make it so you can install to the hard drive, but it looks like Ubuntu is moving this direction as its only installer.
Installing from a running operating system makes so much sense to me that I don’t know why everyone doesn’t do this. You have tons more tools available, and things to do while the install happens. Remember how Caldera used to let you play PacMan while the install was happening? This would let you get work done while the install was happening. What a great idea.
Here’s a review of the LiveCD install of the Dapper Drake beta.