Facebook Page Promoter Lightbox is a plugin for WordPress by Arevico that enables the display of a preconfigured Facebook Page-Like Box inside a lightbox.
Facebook Page Promoter Lightbox in action
Features:
Display the facebook lightbox onload with or witouth a delay
Limit the lightbox to once every $x days for individual visitors
Promote your own facebook fan page
No api key needed at time of writing
Facebook page is needed
Requirements:
PHP 5
Facebook Fanpage
Download and info: http://wordpress.org/extend/plugins/facebook-page-promoter-lightbox/