My latest project has been a display configuration tool, which I alluded to a couple weeks ago:
As mvo had pointed out to me a few weeks ago, the thing that makes coding xrandr GUI's hard is that the useful logic for configuring multi-head's is in the xrandr tool, rather than in libxrandr.
Anyway, the GUI came together pretty easily after I got that sorted out. The tool's correctly reading the outputs, resolutions, and screen layouts via xrandr. Next up, making it apply changes...