In total, the TiltOS for Haiku project has ported over 150 packages to Haiku, all thanks to the Qt port: kchmviewer, kdeaccessibility, kdeadmin, kdebase, kdeedu, kdegames, kdegraphics, kdelibs, kdelibs-experimental, kdemultimedia, kdenetwork, kdepim, kdepimlibs, kdepim-runtime, kdesdk, kdetoys, kdeutils, kdevplatform, kdewebdev, kdiff3, koffice and many others. That's quite the list.
For these packages to work, you need either the GCC4 or GCC2-hybrid Haiku build. You need to install the TiltOS for Haiku package, and then you can use the box utility to install packages using the command line. Most of the ported applications are relatively stable, but there's no guarantee, of course.
More details, and screenshots, are available at the TiltOS website.