I’ve recently been playing around with Slax. It’s a really small, compact yet attractive and very functional version of Linux that fits right onto a single CD-R. (In fact it will fit onto a large USB memory stick as well!) The best feature by far is that it runs off the CD so no installing is required and... This is quite rare for a Live-CD, is that it looks pretty flash too!
There are a couple of different flavours of Slax for download. My favourite is the server version which is really useful for web developers as it contains Apache, PHP 5 and MySQL already set up from the moment you boot up. There are other versions too including a “KillBill” and “Popcorn” version.
Something that is particularly important for me is that an operating system must look good. Slax is no exception and looks really polished... just check out some of the screenshots! Anyway, you can download it from the Slax home page.