How does stumbleupon work?
 

How does StumbleUpon work?

You can register for their site and add your url along with a review. You can also get free promotion of your links by using their url shortener at su.pr. Within a couple of days I got 2 hits to my site just by using the url shortener. All you have to do is to add your blog sites or website's URL and description. It is a website were your viewers have about 5 sec to give your page a thumbs up.

When we first started using StumbleUpon 3-years ago, we weren’t afraid to give a post a thumbs down. This doesn’t mean that StumbleUpon is going to penalize said article, it means that it is not going to send you those types of posts anymore.

The key to StumbleUpon is that its users can share interesting Web content. When they find something they like online, they have a Web-based outlet through which they can let others know about the site. Other users can then view that content, through topic-orientated browsing or purposeful searching, and reciprocate the favor by sharing their own interesting finds.
In this way stumbleupon share the interesting content and do viewing boost to your content.

Know more: http://computer.howstuffworks.com/in...tumbleupon.htm

It is an awesome site where you can share links of any website or content which you like, you can also promote your website on stumbleupon.