WordPress eCards is a premium WordPress plugin used to send electronic cards to friends. It can be implemented in a page, a post or the sidebar.
Download: http://codecanyon.net/item/wordpress-ecards/1051966
More info: http://getbutterfly.com/wordpress-plugins/wordpress-ecards-plugin/
Screenshot: http://getbutterfly.com/wp-content/uploads/2011/11/eCard-frontend.jpg
The update brings members only restrictions and several UI changes and tweaks.