I just recently started using WordPress SEO by Yoast. It seems that I am a little late in the game as there has already been 4,298,169 downloads of this plugin. If you haven’t started using it, you may want to check it out. Be sure and take the tour as it gives a good guide on getting started.
One of the neat things about this plugin is the Snippet Preview that appears below your post. It give you a good idea on how the search will result by the user and indicates whether you have included the proper tags and descriptions in the setup. It provides space to add a Meta Description.
Chuck