After a long period with no Qt4 support for Ruby 1.9, the qtbindings gem has stepped in to fill the void. This project packages the qtruby4-qtruby library from the korundum project, so the API is unchanged.
Installation is straightforward:
sudo gem install qtbindings
or for rvm users:
sudo rvm gem install qtbindings
Compatible with 1.8 as well.