Widgets, Profiles, YDN and Mobile, in the last 2 years. And those are just the ones that I know about because I worked on them. YAP was also new hardware but it was also a new product.
Also, the new Buzz site used all new hardware (and was a new product) and Games rolled out on new hardware when it was upgraded from HF2K to PHP. The old servers were reimaged and folded in with their PHP siblings once it was clear that the build was holding up properly.
