A while ago I already managed to compile gqrx on OSX, but then Alexandru Csete decided to move on to a new audio backend called pulseaudio. Sadly there is no proper pulseaudio port for OSX. Thus I bring you my branch of gqrx 2.1 which runs quite well on OSX.
It contains all the rtl-sdr, gr-osmosdr, GNU Radio, libUSB, boost and Qt dependencies so it should work out of the box. Feel free to contact me in case you encounter problems. I built it on OSX Lion (10.7), and people on Reddit reported it running well on OSX Mountain Lion (10.8). I assume it also runs on Snow Leopard (10.6), though I don’t know for sure. Sadly Leopard (10.5) isn’t supported due to Apple breaking binary compatibility on 64bit binaries for some reason.