>>1
There's also of course these:
http://www.gumstix.com/
Something like this would be even smaller I guess, but it's not a usable system by itself. (System on Chip)
http://www.linuxdevices.com/news/NS9647663764.html
> Linux runs on more architectures than NetBSD
Or rather, you can get some form or derivative of the Linux kernel running on more architectures, with one userland or another. With NetBSD, you get a system built from the official source tree, no patches, running. Of course, if a system vendor ships a Linux based OS image and it's good for what you want to do, no problem.
> the GNU-variants being better in all practical respects
Haha, no. It's mostly a matter of preference (and licensing).
> The only practical reason to use NetBSD is if you hate freedom or penguins.
Or if your company is not OK with the terms of the GPL and want to make private modifications. Or if you want something that is easy to port (as opposed to already ported). Or if you want to use the same driver source across multiple architectures. ...
Basically, it comes down to what it is that you want to do. Just saying "A is better than B" with no context is stupid.
Of course, QNX is way better than either for small systems.