If you want a quality video that people will actually sit through and watch you need a gopro or a ContourHD. There really isn't any other options. They are the only 2 cameras that can take a direct hit and keep on keepin on.
As far as the best way to mount it, there really isn't a way to do it that doesn't get in the way or stick up or out in some way. If you want to film and use a quality camera it is something you need to deal with.
I personally am not a fan of headcams. The gun gets in the way, it's pointing all over the place, and you don't see what you are shooting at. The mistake I feel a lot of players make is they play exactly the same with the camera as they would without it which leads to jumpy unstable bad video. I use a barrel mount and make a point to run around with my gun up as much as possible.
There are different ways to use the camera depending on what you are doing (obviously) The best way? Buy 2
1 on the gun and 1 on your head and edit the videos together.
I've posted this vid in another thread: