Zivvys - Follow and Share local news just like you follow people on twitter.
RailsWizard - A step-by-step template generator for Ruby on Rails applications.
Foosleague - A Foosball "league" tracker for offices and bars.
Monday Calendar -- The most advanced calendar on the planet. Handles todos, appointments and events side by side super conveniently.
Using OmniAuth with Devise from @plataformatec for user signup and signin via Twitter and Facebook. And using omniauth-google-oauth2 by @zquestz for connecting to Google for full calendar sync.