Certified on HP Servers (sort of)
I was waiting for Ubuntu to be certified on HP iron in the form of a Ubuntu version of their Proliant Support Pack. I honestly believed that Ubuntu would have to start rolling their own kernels as Rehat and SLES do before that would happen, but I just checked, and it's there: version 8.32-1 from the 14th Jan 2010 as well, even more up to date than the Redhat kit. However none of the long list of individual linux drivers kits are available yet. Good progress though.