DNUK are an online UK store selling desktops and servers with a specialisation in virtualisation. The desktops have a default configuration of Ubuntu pre-installed but you can specify full frontal nakedness if you prefer. Other options are OpenSUSE, Fedora and Debian on the desktops and aditionally CentOS and Scientific Linux on the servers.

Naked Computers is hosted by The Open Learning Centre as a service to the community
I’ve bought three computers from them. All came with Debian installed -just so they knew it was all working and I had something to play with when they arrived.
They were happy to tweak the configuration as I requested and seemed nice enough people to deal with.
Two Iiyama TFT minitors needed swapping under warranty and that was all done without a problem.
I have purchased several servers and a few desktops from them. The most recent being a desktop at the end of 2009. They are a pleasure to deal with and every single machine I have bought has worked as required out of the box. The build quality is excellent as is the customer service.
They custom build your machine so don’t expect delivery the day after you order. Two weeks is about the norm but it is well worth the wait.
Highly recommended.