Twitter added a new feature for website owners yesterday. The Tweet button allows you to embed a small pieces of code in your site that will allow twitter owners to tweet your page to their followers, big deal you say... I can already do this, true but the difference in this button is that it embeds your twitter username in the tweet and launches a new overlay page that then keeps the reader on your site. A small but powerful step forward for site owners, IMHO. See twitter's video explanation:
...and here it is, give it a click!