One of my favourite ways of learning something about existing code is to load it into irb and play around with it. You are able to ask every object in irb what it can do. It is as easy as you just asking for methods or public_methods and the object will show its abilities. But often you get spammed by Object or irb methods that you rarely want to use.

More solutions for the projecteuler.net problems. Some of them are solved using 1.9.2 features.

One useful (and funny) feature of Ruby is the Symbol#to_proc method that lets you write concise code like this: %w|1 2 3 4|.map(&:to_i). Almost everyone who knows this feature loves it ;). However, the use cases are pretty limited, because in most cases you need to pass parameters!

has_many_booleans is an ActiveRecord plugin which creates virtual boolean attributes for a model. When the object gets saved, the plugin transforms all attributes into a single integer, using a bitset. So you can easily add new attributes without changing the database structure.

In Ruby, dealing with Arrays and similar objects is pretty fun. And we have gotten more possibilities with Ruby 1.9.2 :)