Social bookmarking sites like Stumbleupon can be a good source of traffic. However, spamming [posting your site's URL repeatedly] will prove to be counter-productive. Getting traffic from the site needs a two-pronged plan. 1. To get something you need to give something. You need to be active on Stumbleupon. Upvote content that has been submitted by other bloggers. More upvotes means a submitted post will be seen by more people. That [upvoting the posts of other bloggers] will get you "friends" who will reciprocate, driving more traffic to your site. 2. Facebook Groups There are a number of Facebook groups that bring together people who intend to promote their blog posts on Stumbleupon. Join these groups, help each other. If you've got 20 people sharing your blog posts on Stumbleupon each day, you could get up to 100 unique visitors landing on your site every day. All the best.