Good applications to learn from

Hello-

I was wondering what open-source applications the group feels would be
good ones to look at for someone new to Ruby on Rails (but not
development). Ideally, I'm looking for something like the Microsoft
ASP.NET Starter Kits. They are complete, non-trivial applications that
embody idiomatic use of the platform and best-practices while not being
overwhelmingly complex. Any recommendations?

-Eric