This WordPress plugin creates the meta keywords tag and the meta descriptions tag for single posts automatically, simply add the tags <MetaMagic>some text in your post</MetaMagic> while in the WordPress Editor(Text Tab) and that will be the meta description tag content. The meta keywords content is generated from the tags in your post. In the Settings Panel you can toggle meta keywords tag only, or meta description tags only, or both, or none. Using the method of tags (<MetaMagic>a phrase in your post or page </MetaMagic>) will allow you to preview your page source, so that you can view your new meta description and meta keywords, once you click publish, the tags are removed from your post, but your meta description & meta keywords are now in your new blog post.
Was able to install quickly without problems and I could add meta tags to all my pages without editing them all. Cool plug-in, really saved me some time.