I do a lot of modeling with mesh that has rectangular faces. I would like to unwrap them and then align the four corners of my faces to the four corners of the UV image. I simply want the entire image to cover each face completely. It is easy to select each of the four verts to move them to the corners, but is there a way to get them to snap to the corners?
You can check Constrain to image bounds option in the UVs menu:
Then you can scale your UVs as long as they take less place then the texture space. When they meet the boarders you'll no longer be able to scale them up.