This gem is a great example of how an open source project started way back in 2005, has evolved over time thanks to the active Ruby and Force.com community. The gem, written to leverage the Force.com and Database.com REST APIs, has been designed to be independent of web frameworks (Rails, Sinatra etc.) to allow developer freedom when designing Ruby-based apps. What’s more, with full support for the Chatter REST API (Note: The Chatter REST API is still in developer preview, and subject to change), building Chatter-based social apps in Ruby has never been easier.
If you are attending Dreamforce this year, I highly encourage you to attend the Building and Deploying Great Applications with Salesforce, Ruby, and Heroku in the DevZone lightening theater at 5:00pm on Tuesday. This session, presented by the authors of the gem, Danny Burkes and Richard Zhao of Pivotal Labs, will give you everything you need to get started building apps that connect to Force.com and Database.com.