TempleOS has various impressive features.
http://www.codersnotes.com/notes/a-constructive-look-at-temp...
TempleOS is a hugely impressive one-man project, but it's a standalone OS with no networking.
There are other tiny OSes which are FOSS and are much more capable.
Oberon is my personal favourite, in terms of how much it does with how little. http://ignorethecode.net/blog/2009/04/22/oberon/
There's networking now.