This plugin by Ahmed Hussein adds the new and the official tweet button to your WordPress Blog is now as easy as a cake. You can use shortcuts [tweet_vertical] [tweet_horizontal] [tweet_none] or PHP code.
Features:
3 Shortcuts to add the buttons manually.
Complete Settings Section.
Live Preview in the Settings Section.
Requires PHP 5
Plugin homepage: http://blog.ahmedgeek.com/the-official-tweet-button-plugin-for-wordpress