This plug-in adds the post thumbnail of articles to the RSS and Atom-Feed via Media RSS specification.
Adds <media> tags to your feeds with post thumbnail support which came with WP 2.9 version. This plugin is based on Andy's (http://andy.wordpres
Adds MediaRSS to your RSS2 feeds. The first image in a post will be the post's thumbnail on services that support it (e.g. FriendFeed)