Digg is a popular user drive social network. ProNet Advertising wrote up a nice Beginners Guide to Digg.

If you have ever felt like you had to dig around the Internet for good content, you might want to look at something called Digg (digg.com). Digg is a site that will help you avoid the process of digging and instead, get exactly what others have dug up so you can see some of the great sites/stories/things out there on the Internet. Many people reading this might already know what Digg is all about so if you fall into this category, quit reading now and go elsewhere or you might feel this is a bit basic. If you haven’t heard of Digg, read further and you can not only understand one of the more successful sites on the web these days but also get an idea of how you can leverage it for your business. Digg epitomizes the value of collective intelligence and community on the Internet in a way that not only brings value to its users, but also to businesses that are savvy enough to take advantage.