If I remember correctly Python ships with
Tk as it's standard framework. What's Ruby's default?
Ruby uses Tk as well.
Ruby ships with the tk libraries. Also available are fxruby
is quite popular and shoes was gaining some momentum until the authors mysterious disappearence. Of course there are Qt libraries available as well.
There are quiet a few libraries. Most known are: - tk (as mentioned earlier: http://www.rubycentral.com/pickaxe/ext%5Ftk.html) - gtk (http://ruby-gnome2.sourceforge.jp/) - fxruby (as mentioned earlier: http://www.fxruby.org/) - qt (http://techbase.kde.org/Development/Languages/Ruby)
Shoes doesn't deliver a gui library. It is more like a cross-platform framework to build light-weight gui-applications. On linux it uses gtk-libraries.
There's a nice framework for building gui-applications: Rugui (http://rugui.org/). It is a framework for bigger applications and it copies the Ruby On Rails way of working. It supports an MVC design, gui & qt and Rspec & TestUnit. Worth looking at!