Recompute goes to considerable lengths to make a computer that is as recyclable as they can make it. (Yes, those babies are cardboard). They may not look sleek, but they are state of the art personal computers and they are highly customizable. If you are concerned about e-waste and want to do something about it, you should really give them a look.
Go to their site and read more about them. I am not endorsing them and I haven’t seen one in action, but I am always happy to see IT companies – including the one I work for – striving to make computers that waste less resources.