I’m still getting up-to-speed using Rails (4 months in and counting) and I’ve found some great resources which have helped me kick-start the process and tackle the steep learning curve of using a totally new development language/environment:
1) Ruby on Rails Tutorial (RailsTutorial.org) – I spent the week before starting my current (and first) job using Rails by literally consuming all I could from this site. It’s great for learning Rails 3 from scratch. I love the approach of having both a book and screencasts which cover the same basic material but with a slightly different approach. The author Michael Hartl really knows his shit and has put a lot of thought and effort into the material. By working through the tutorial to the end, you will have built a fully-functional Twitter clone (you can view mine here).
2) Ruby Koans (RubyKoans.com) – A great resource for learning Ruby from the ground up. On top of helping clarify a large number of areas in the language, the Koans are really fun to run through. They take the form of a bunch of unit tests that are broken, which you need to go through and fix, learning some piece of Ruby functionality with each one. A lot of RoR sites/books focus more on the Rails side, but the Ruby side is equally important. I really got a lot out of running through all the koans and it helped me look at elements of the language in a different way.
3) Various projects on GitHub – There’s no better way to get proficient at something than to have a ton of good (and bad) real-world examples to look through and that’s exactly what GitHub provides. You can check out code for all the gems you use everyday – looking at every commit and letting the code tell the story of how it came to be in its current shape. One of my coworkers suggested this approach and it has been awesome.