I'm always looking for a new way to mount my GoPro cameras. Mic stands are plentiful and relatively cheap so I thought why not create a simple mount that would screw onto a mic stand.
At first I considered creating the entire thing from scratch. This would require a threaded brass insert, some sort of locking bolt, and lots of time trying to get all the tolerances just right. So, I poked around to see how much a cheap mic clip would cost. I found one on Amazon for $2 with free shipping. You can probably find them elsewhere as well.
There are two options with this thing. You can build it as is using the specified mic clip or you can use your own clip.
Build As Is
If you want to use this thing as is, you just need one item (besides this thing's STL file):

• Musician's Gear Heavy Duty Basic Mic Clip, part #: MS103-MG
  Use A Different Clip
  If you want to use a different mic clip, you will need two items:
• Your mic clip of choice

• GoProHD Mount (Female) aka thing 6154
  You can customize this thing in the customizer but it will look weird because the necessary include for the GoProHD Mount will not there. So, you will only see the bottom of the mount in the preview.
  Alternatively, you can just download the scad file and the GoProHD Mount and adjust the values yourself as needed.
  Alternatives

  I elected to use the standard GoPro quick connect so it would be easy to attach and remove the camera as needed. This also allows using things like the GoPro flexible 'goose neck' attachment as well.
  One could obviously build this using just the standard GoPro 3-finger part instead and directly mount the camera case or other parts to the mount.
  Another option to consider is rotating the GoPro mount 90 degrees with respect to the mic clip so that the two axes (yes, that is the plural of axis, look it up) of rotation, one through the mic clip and the other through the GoPro mount, are orthogonal to each other. That way you get an extra axis of motion without having to add a 90 degree GoPro extension in the middle. This presents some interesting issues with printing however. I'm not sure how it could be printed successfully without support.
  A final option would be to print the thing in two parts and assemble it after printing (or even print it with a ball joint in between). This would improve print quality but might create weak spots at the joint.