Tuning Forks
 

What specific catagory would this fall under?

Sound does have theraputic qualities. I have seen people playing with those solfeggio scale forks. Anyone use this stuff?

Sound therapy / chakra therapy .
Yes I have used them in the past but I don't have my own set .

Although I'm not familiar with what solfeggio scale forks are, I do believe sound has value for therapy of many kinds. It must have to do with our spiritual vibrations - or at least that's my opinion.

I like a few audio CD's from Dr. Jeffrey Thompson - who works with sound: The Awakened Mind System, The Alpha Relaxation System, and Sleepy Ocean (never sleep without it). I really would like to know more about other sound/music that can be found to help with healing etc.

Maybe another good example would be the Singing Bowls? Some also use these to cleanse your cystals/stones, too.
This is a nice short overview of singing bowls and other instruments being used in various ways:
http://www.youtube.com/watch?v=Bpw53tN6h8E