That is the HTC Sense Clock which is only available on HTC phones the the Sense UI. You will not be able to get that exact clock, but the widget called Fancy Widgets looks nearly identical to it. Fancy Widgets is not available in the market though, so You are going to have get the application file from someone else as I am not sure if you can download it from their website. There is also beautiful widgets, which has many skins that makes the clock look like the HTC Sense clock, and beautiful widgets comes with many more widgets.