Use quaternions/remove gimbal lock from blender view This took me a while to find so I'm adding it here.

I was trying to use the Project From View UV Unwrap and because 1. there's no way to roll the view camera and 2. the camera gimbal locks at the poles I was having a lot of trouble getting the correct direction to match my texture.

The answer is of course to put the camera in quaternion mode, but I had no idea how to achieve this. There's the Transform Orientation selection box which has the Gimbal option but this is not for the camera's transform.
What I wanted was to change the TrackBall/Turntable option in File-&gt;Preferences-&gt;Input

(source: blender.org)
Also see:

What is the difference between the trackball and turntable style view modes?