Compact gem or libraries for improving Ruby skills?

I'm an advanced beginner/intermediate Ruby programmer. I'm really working on improving my Ruby skills, with specific focus on writing more efficient, compact, idiomatic Ruby, following solid testing practices, and learning and adhering to project structure and other general best practices.

With that in mind, I've been looking for good material to learn from. I've checked out a couple of the Play B开发者_StackOverflow社区y Play Peepcode screencasts, which are great, but not exactly what I'm looking for. I've poked around Github, but most projects that I'm familiar with can be pretty sprawling--I spend far too much time unwrapping how things actually fit together and trying to build a mental model of things than I do actually spending time understanding the development process. So, I'm looking for good examples of quality projects/gems/libs that are compact, well-built, etc. I'd prefer something that's self contained, i.e., doesn't extend functionality of some other tool that I would first need to pick apart before being able to understand the 'extension'. Also, my focus here is Ruby development--not Ruby on Rails development. Any suggestions?

You sound like a great candidate for taking Ruby Mendicant University's core skills course-- it's aimed at intermediate rubyists looking to improve just the skills you've mentioned. I really recommend that you check it out (I'm an alum).

Even if you don't take the course though, the exercises for the course (which can be somewhat contrived) and all the student projects (which are real-world projects) have been released. These have all been written by students at about your level being mentored by more advanced people with a focus on making the code more idiomatic and following best practices.

The best resource I've found is Eloquent Ruby by Rick Olsen, which is an in-depth guide to writing idiomatic Ruby, and the reasoning behind the choices made.