PowerInviter is a WordPress plugin by powerinviter that represents a new generation of “Tell a friend” programs with many additional “PRO” features and viral marketing principles: an extremely easy way to convey a message and get a reward for the action.
PowerInviter creates motivation: people will get gifts for their recommendations! It is precisely this fact that explains the MULTIPLE EFFECTIVENESS of PowerInviter as compared with other “Tell a friend” solutions.
This plugin allows people to recommend any page (post) to their friends with the title and short page description (teaser). It is fully integrated with the http://www.powerinviter.com online service, so you do not need to place any html code into your PHP templates.
Download and info: http://wordpress.org/extend/plugins/powerinviter-ultimate-tell-a-friend-tool/