I'd like to build myself a little linux box. Something to tinker and learn with, but mostly just to get on the net, watch some youtube and leave my messengers up 24-7. Basic stuff.

But I don't need one of these hulking towers or re-purposed old machines that suck power and take up tons of space.

What kind of hardware should I look for to get a little linux box with a lightweight power-consumption profile? Is there a particular "green" hardware vendor out there the community likes? And monitors... Well, maybe my monitor doesn't have to be THAT green. I still love 19"+ widescreen dealies...

Any recommendations for low-profile, low-consumption boxes suitable to linux? And which distros do you think I should be looking at? Xubuntu, because it'll be light on hardware and resources (probably?) ?