Goldberg is a lightweight CI server written in Ruby which worries about Bundler & RVM so that you don't have to.
Modified soap4r library to run on Ruby 1.9
Making HTML emails comfortable for the Rails rockstars
Ruby libraries for working with Amazon Web Services ( Mechanical Turk )
Flexible authentication solution for Rails with Warden.
ReCaptcha helpers for ruby apps
Mock SMTP server for development/testing. Save SMTP requests as HTML.
Mail Magnet allows you to override e-mail recipients in ActionMailer so all mails go to a given address.
webrat alternative which aims to support all browser simulators
SitemapGenerator generates Sitemaps for your Rails application. The Sitemaps adhere to the Sitemap 0.9 protocol specification. You specify the contents of your Sitemap using a configuration file, à la Rails Routes. A set of rake tasks is included to help you manage your Sitemaps.
simple database import/export app
The facebooker Rails plugin
Devise << Facebook Connect. IMPORTANT: Not maintained anymore.
A Ruby wrapper for Sendgrid's Web API.