Ballhype lets you submit any kind of story you want to publish. This page has quite the same goal than Twitter and Mixx: promoting your articles or any interesting story you find on the web. For submitting a story there you need to create an account there, and then you add one. Kept in mind that Ballhype only accepts sport stories. Other sites like this are the reviewed in the next links:

http://hubpages.com/hub/www_twitter_com
http://hubpages.com/hub/www_mixx_com