Judging by the look of it, it resembles Google Gadgets, but if you look on his system tray there's the Windows Gadgets icon, so he's not using the Google one.
To get more gadgets, open the "Gadgets" window on Windows Gadgets and click "Get more gadgets online", or click this link to go to the website.
(This is yet the same link for Windows Vista and Windows 7)