I have need to mount a motor to a shelf without using any fasteners.
This thing is a notched sleeve that will fit a nema 17 motor snugly. Of course there's an OpenScad file, so you can size it to whatever you want.
It fits nicely with any 'keyed' item of the same size. I am using it with this keyed shelf UClip: http://www.thingiverse.com/thing:5968
It works out fairly well, and the friction fit can be enhanced by fasteners or glue if you really need that.
I did just create another motor mount: http://www.thingiverse.com/thing:5940 but that's the more typical faceplate with screws, and screws to attach variety. This one is all about not needing any fasteners.
1) Measure your motor. If it's not 42mm square (roughly nema 17), then change the OpenScad file to fit whatever size it is.
2) Print out the mount.
3) Slide it onto the keyed thing you want to attach it to
4) Slide the motor into the mount