One interesting thing about the software world, I find, is that there is a trickle-up system for innovation. Things like live searches, better task bars, and the much-debated widget/gadget/dashboard idea often have had their seeds in smaller OSes or pieces of software. Designers will find a way to work something in their program that others may be able to adapt to something bigger, and thus the snowball begins to grow.
Some of the OSes (perhaps more accurately called Desktop Environments, says a commenter at the link below) on this interesting list may be familiar to you, some not, but doubtless all are interesting and relatively unique in their strengths. I’m far from an expert in this field (in fact, it would be a stretch to call me a dabbler), but I think I have the appreciation for usability and good design that comes from a lifetime of using computers and technology of all kinds.
This list at Royal Pingdom is an interesting one, but I think it focuses on actual alternatives to Windows and OS X — as in, things that do what they do, but in a slightly different way. The word you see repeated often is “lightweight,” and indeed, placed next to either XP, Vista, or OS X, nearly any operating system is lightweight. The idea behind many alternative OSes is trimming the fat, or more accurately never accumulating fat in the first place, unlike the industry leaders. If you don’t game or work with high-requirement media like video, RAW photos, or 3D models, there are many ways to satisfy your needs without spending a dime or installing more than you need. I had hopes that Windows 7 might have this virtue (per rumors that it was to be a very modular OS) but those hopes have been squashed.
Minix
Menuet
Menuet and MINIX3 provide extreme examples of this, attempting to trim all the way down to the bone. Menuet will fit on a 1.44MB floppy, and while MINIX isn’t nearly so frugal in its distro size, its kernel is extremely compact and reliable and the system is spec’ed to run all the way down to 386s and super-limited embedded systems. Apple is cutting down on bloat with Snow Leopard, but how amazing would it be if OS X were fundamentally small — to say nothing of Vista.
SkyOS
Syllable
ReactOS
Ubuntu
Setups for really basic computing like Syllable and SkyOS are probably Davids to Ubuntu’s Goliath at this point, but if the basic organization of *nix systems isn’t agreeable to you (or your Mom), maybe an Amiga-based or from-scratch OS is another way to go. And if you like Windows but don’t want to give your cash to Microsoft? Try out ReactOS and donate a few bucks for a bunch of guys trying to do everything Windows does right and (I assume) none of the things it does wrong.
Plan 9
But these changes might not be drastic enough for you. A commenter at the list points out (perhaps rightly) that the “OSes” mentioned are really just replacement desktop environments, that change nothing about the way the system really works. I would counter that that’s because the system they use does work, but it’s worth keeping an eye on some of the more drastically different OSes currently in use. Plan 9, for example, has a fundamentally different approach (if I understand it correctly, and I doubt I do) in not having a separation between applications and files. Files interact with one another through shared commands and there is no “application” layer to deal only with one type of file or another. I’m not sure I’m getting it right, and if it sounds strange, that’s because it is. It’s a totally different way of computing and it should seem strange. but so many of the things we use today without thinking about them were pure fantasy a few years ago.
It’s an exciting, ever-changing world, this one of niche OSes and freaky desktop replacements. Maybe in one of them will we find the features we all yearn to be integrated with our more traditional desktops: centralized application distribution, low-level file interoperability, a UI designed from the ground up to be customizable, and so on. If something like Ubuntu can throw sand in the face of both Apple and Microsoft, who’s to say who the next little guy will be who grows up and takes on the industry?