No 2. TweetMeme Button

Used by some of the biggest websites like CNET.com, Wired and Break.com, this plugin allows easy retweeting of you blog posts. It also gives you the ability to control the length of the tweets. Furthermore, it also features live count of the retweets of your page.
Go here to download.

No 1. All-in-One SEO Pack

This plugin will automatically optimize your blog for the search engine to the fullest. It allows you to customize the post title, post description and post tags for all the posts individually. Furthermore, this plugin also features advanced canonical URLs and built-in API.

Go here to download.