on my desktop computer i use Ubuntu, it's the OS thats worked best for me so far, but when i get bored install stuff to try it out, i have all my stuff backed up on a USB hard drive so i can install a new OS i won't lose it (and yes i know that you can partition the drive so that the OS is in a separate partition from your documents and you won't lose a thing if you change the OS, I've just been too lazy so far)
as for my School-issued laptop i use a puppy linux boot disk. the school has windows XP installed, that operating system combined with the way they set it up does not suit my needs in a few ways. they aren't powerful computers so they aren't too fast. several features are disabled (including right-clicking... yea, dumb i know) and the sound drivers were deleted so we wouldn't listen to music. and we're restricted from installing programs. Puppy linux on the other hand is very small, saves your settings to a file, loads completely to RAM so you can remove the boot disk and use the disk drive, it has sound (of course) and its FAST!!!
puppy also offers several versions or "puplets" including different programs and features like wine, you can find almost anything you need in a puplet, or you can remaster the disk and make your own puplet with your own feature set... basically it just made my school laptop more useful for me.
www.ubuntu.com
http://www.puppylinux.org/