Invite Widgets

Non-developer trying to locate some widgets or recommendations for products that allow a user to invite friends from FB, Twitter and E- mail for a site built with RoR that utilizes FBs OpenGraph.

Mainly looking to find some widgets or locate documentation for creating invites for FB and standard e-mail services (gmail, yahoo, hotmail, etc) rather than using SaaS as we've already built our own login/registration and invite solution and would prefer to modify and improve on it.