A buddy of mine who's employed at the local shooting range turned me on to this line of holsters recently.
It is by far the most comfortable holster I have ever worn. It stays put, even when loaded with my full-size M&P9 (unloaded of course) with running and jumping around. It makes my full-size M&P9 disappear, even in such simple clothes as a white T-shirt or a light-colored polo shirt. And at $30, it's hard to beat! I would highly recommend to anyone.
Home of the Original Remora No Clip Holster