No 6. Sociable

This adds social media buttons, including twitter, to your blog with the convenience of, well, anything. It installs easily and blends in seamlessly.

[youtube]http://www.youtube.com/watch?v=wCJnbB8pQA0[/youtube]

Here is the download link.

No 5. Twitthis

This allows your visitors to share your posts with their friends with their own personalized messages on twitter. It converts the URL of your page into a small one and adds it to the description which your visitors will write.

Here is the download link.