Are you familiar with the website StumbleUpon.com? It's an internet community website that lets users vote on and share content with others. It also automatically shows you content it thinks you'll like.
The people who started it sold out to ebay, then bought it back. They've made lots of improvements since then.
Like most of the social web, StumbleUpon can help you get lots of new links and website hits you didn't have before...but only if you've got cool content because, as you know, people are apt to share content they like.
Also, when people are "stumbling" through the site and across your content, they might share it through other social sites like Facebook and Twitter. So you can why some people see hundreds of thousands of new visitors to their websites in a single week.
If you're not using StumbleUpon, give it a try. And watch this video for more info about how it works and why it's more effective than ever.