Putting a "Tweet this" button on your blog post makes it easy for your blog visitors to share your posts on twitter. Which in turn brings traffic to your blog. How much traffic it brings depends on how popular the person is and how many people follow his/her tweets. But it is always a good idea to make it easy for your blog visitors.

Add the following:
<div style="float:right;padding:4px;"> <script type="text/javascript"> tweetmeme_url = '<data:post.url/>'; tweetmeme_source = 'your_twitter_user_name'; </script> <script type="text/javascript" src="http://tweetmeme.com/i/scripts/button.js"></script> </div>
just after:
<div class="post-header-line-1"></div>
Credits: http://help.tweetmeme.com/2009/04/06/tweetmeme-button/