I would just like to share this knowledge with anyone who isn't aware.
It seems that not many people are aware of this, but WP.com has implemented the Tweetmeme code onto their site. So to use it, all you need to do is use this shortcode:
[tweetmeme http://www.URL.com]
*if would like to specify you twitter name, include this: source=”your_twitter_name” (Keep the quotes)
In that case, it should look like this: [tweetmeme source=”your_twitter_name” http://www.URL.com]
*If you would like for the button to appear on the home page and not not only the single post view, the add this: only_single=false
Altogether, it looks like this: [tweetmeme source=”your_twitter_name” only_single=false http://www.URL.com]
Hope this helps someone!