Certified Hardware page on their site! It shows different Original Equipment Manufacturers (OEMs), along with various hardware components (video cards, wireless cards, web cameras, etc. The site breaks it down so you can find a desktop, laptop, netbook, or server and which version of Ubuntu works with which hardware.
So, if you in the market for a new system, and your interested in giving Ubuntu a spin, I recommend using that list as a guide.
In the Love of the Three in One,
Jack +, LC