This will be the first plugin I will publish, so it will be a little simple and maybe unpolished.
I built this plugin because I see that all the links posted in twitter are shortened by bit.ly or a similar service. There are many plugins that insert at the bottom of the posts links to share the post in various services but the link sent is not shortened. By default a long URL sent to twitter is shortened using bit.ly but one of the useful features of bit.ly is that you can get statistics of how many clicks the shortened URL received, from where and when.
How to use it:
Once you have installed and activated the plugin you have to enter your login and bit.ly API key in the ‘Bit.ly Share Links Options’ page and select what short URL you want to use (bit.ly or j.mp) and if you want the links to open in a new window/tab.
Now when you publish a new post the plugin will send a request to bit.ly to generate the short URL and store it in the post meta. When a user goes to the post page at the bottom of the post the plugin will insert links to share your posts in the most popular social media sites (facebook, twitter, stumbleupon, etc..).
If you have the sociable plugin installed the plugin will not display a second set of links, instead it will hook into the sociable plugin and replace the long URL with the short url generated by bit.ly.
The plugin also retrieves the stats for the short URL, you can see the stats in the edit post page.