I read a short time ago that the Metasploit project (http://www.metasploit.com/) is the largest ruby project out there. I've tested it a little and it has a lot of Ruby code. Would you recommend that as a project to look at as a Ruby and Ruby metaprogramming example to learn from?
I would begin by looking at small libraries. One of the nice things about Ruby is that there are so many gems around that are popular and useful, but still tiny. For example, if you want to see a lot of metaprogramming going on, look at _why's Camping web framework (install with ). Most good libraries use at least some metaprogramming tricks, so just pick your favorite gem and peek into the source.
Once you can wrap your head about small libraries, by all means move on to the Rails source to see something (way) larger.
Paolo Perrotta, Europe
Author of Metaprogramming Ruby