I'm about to start a project developing a Ruby desktop application. I expect to to be fairly big and I want to learn techniques for dividing code among modules and other techniques for managing complexity. Most large apps I've looked at are Rails apps, but these aren't very helpful, because most of the work is done by Rails itself.
What source code would you recommend I take a look at? I'm not interested in libraries or Rails apps, because I get how they do things. CLI apps are OK, but I'm mostly interested in GUI apps (I'm using Gtk+, but I can learn just as much from apps using other GUI toolkits).