A great example of how LiveCDs can be used, this programming book comes with an Ubuntu LiveCD with all the code examples and code editors installed and ready to use.
There’s a live CD included so you can boot up Ubuntu Linux and see all the projects – not only view and play with code snippets via the Bluefish programming editor (noticeably superior to the text editor I’ve been using to write my PHP), but also running the final applications off the disc.