That looks more like a digg clone. If you would like to build something similar i can say this digg clone script does the job perfectly.
Edz is right. It's not really blogging software as much it is Digg-like. I wrote it from scratch in Ruby on Rails. I didn't look at Pligg, but if you want something similar, it seems like it does a pretty good job. There are plenty of sites that are running on Pligg. If you don't want to do any coding yourself, crispynews.com appears to have turn-key sites you can start.