Like Buttons

Like Buttons makes your site instantly share-able. The plugin adds tags to your pages’ HTML which will pull the proper content from your site when someone shares one of your site’s URLs on Facebook. Using some simple Theme functions, you can add Like buttons to posts / pages / custom post types AND a Like button for your blog / website

// in the Loop - for posts / pages / custom post types
the_like_button()

// a Like button for your blog / website, put it anywhere!
the_blog_like_button()

// use this if you don't want to register your app
the_like_iframe()

Read More: http://scottctaylor.wordpress.com/2011/01/04/new-plugin-like-buttons/