Well,
I'm not sure what u mean as a NOS.
Everything is NOS nowadays, windows, Mac, linux, they all support networking capability. Is that what you mean, you want a linux that is capable of surfing the net for instance?
I suggest you read on linux. First of all. You dont actually only download a kernel. You need to download a distribution...
A linux distrition is a linux flavored system.
A distribution analogy could be seen like this: Windows 95, Windows NT, Windows Me, Windows 2000, Windows XP, and soon Windows Vista...
They are all different, but underneath they are all a windows kernel. Most of these Windows do the same thing but each one has it's own speacial things it can do they other dont...
Soo, a linux distribution, a linux with a different taste of it..
A little list of distributions: Red Hat's Fedora Core, Mandrake, Suse, Knoppix, there are 100's of those...
The mostly used and the one you should maybe begin with is Fedora Core...
And Knoppix is a LiveCD distribution. Meaning you dont need to install it on your hard drive like the others, or like Windows. It runs out of the CD. Its great for trying out linux. And you cant fuck up your computer that way... You just reboot...
Forget about the kernel thing, I tought u meant something more specific. I suggest your read on Tutorials about Linux...