This is a handy little program I wrote for tuning an acoustic instrument. There are other instrument tuners on the web, but mine has a few advantages over them. It has the full range of a piano. Also, it has a slick interface that includes a scrolling graphical representation of the pitch you are playing in relation to the pitch you are trying to play and spectrums of the waveform you are playing.
Download Keith's Tuner (MacOS required)