These sites enable you to add links to your stories or blog posts and write reviews on these stories to capture a bigger audience.
Users log into Stumbleupon and based upon their interests are automatically shown blogs and websites that will be of interest to them. I personally have found Stumbleupon an invaluable tool for driving traffic to my vintage fashion blog.
Digg on the other hand is mostly targeted for news or like news stories and has topics such as business and entertainment.
The Digg website says the following about how the wesbite works:
Welcome to Digg.com, a user-driven news Web site that brings together hundreds of thousands of people to do the work of finding, submitting, reviewing and featuring news stories drawn from every corner of the Web.
Similarly to Stumbleupon, users are directed to stories that may be of interest to them based on their interets. Each link uploaded needs to include tags or categories in which the story will fit.
Personally I find Stumbleupon easier to use from a bloggers perspective and I love the ability to add whatever tags you want to add. Digg on the other hand has specific tags and categories you can use with general stories falling under the ‘lifestyle’ category’.
All in all these social bookmarking sites are invaluable resources for budding online journalists who want to be acknowledged. These two websites are some of the most popular and useful social bookmarking sites but there are plenty of others out there in the online world.