I recently installed the plugin Wordpres SEO by Yoast on my this blog, and others. It was recommended by one of those top 10-20-50 WordPress Plugin posts you find all over the place.
You can read more about Yoast and their plugin on their website http://yoast.com/articles/wordpress-seo/
One of the features that comes in handy quite often when writing a new post or page, is the Snippet Preview as seen below:
It hangs out just below the content box when you’re writing up your page or post, and it provides a preview of what your article will look like when its posted on Facebook or other sites that take a preview of your article.