Ubuntu Landscape
Canonical: "Landscape provides users with a hosted web interface on which all machines are registered. From this single interface, packages and security updates are deployed to the entire network of servers and/or desktops with a single click. Additionally a wealth of monitoring data is provided graphically to the administrator showing process and resource use as well as flagging any available security fixes for the system."
Wow. Cool. Seems like a real time saver; currently, when I have to apply changes to a group of machines, I find myself logging in and out of each of them and that's not very funny when you know your server farm increases in size regularly...