WebUrbanist has a nice little roundup of modern musical instruments.
My random commentary:
Electric violin is mentioned by not electric cello.
No Haken Continuum
I keep thinking about downloading Ocarina into my iPhone and forgetting about it.
The Hapi Drum's inspiration, the Hang Drum, was worth a mention. But the Hang Drum is harder to obtain and it costs a lot more, but much of the extra cost is due to the more complex design. This is a nice video showcasing both instruments plus a couple of others:
