Though I'm looking for Rails specific suggestions, I made the question nonspecific as i'm sure a cross-platform list would be beneficial for many of us.
If you want good source code, find the most popular Rails project that interests you. Popular projects usually have a high level of refinement and it being something that interests you will make it a bit more interesting.
As real4real points out, actual coding is important too, make sure to dabble with things you learned and/or if you think of a novel way to handle something try it out on your own and see how it all works.
I think reading through code is a really valuable supplement to the learning process, especially when dealing with a framework like rails which is so heavily convention based. I find reading through code to be the quickest way of exposing myself to the standard idioms of rails based development.
Have you heard of jumpstartlabs? They have an awesome series of tutorials on their site covering stuff like common design patterns to use and how to use workers for background jobs etc.
Also, the project is open source so you can contribute to help improve the tutorials: http://tutorials.jumpstartlab.com