While I don't know of any resources or tutorials, I'm sure you can get plenty of advice and examples right here on the forums. You may find you get more/better responses if you ask specific questions on individual topics.
Most real-time strategy games' cameras are simple things - always rotated so that North is up and tilted a bit so that you aren't looking at only the tops of things. They translate about along the X and Y axis when the player holds an arrow key or positions the mouse at the edge of the screen. The camera stays a specific height above the ground at the centre of the screen - to find the height of the terrain at the centre of the screen, use a LinePick straight down from North of the camera (the more the camera is tilted, the further North the centre of the screen will be), to which you would add your camera_floating_height constant.
Unit selection typically involves allowing the player to click on an individual unit or drag a rectangle around several. CameraPick solves both of these problems: finding the unit under the mouse or finding the start and end points for the rectangle on the terrain.
Most real-time strategy games' cameras are simple things - always rotated so that North is up and tilted a bit so that you aren't looking at only the tops of things. They translate about along the X and Y axis when the player holds an arrow key or positions the mouse at the edge of the screen. The camera stays a specific height above the ground at the centre of the screen - to find the height of the terrain at the centre of the screen, use a LinePick straight down from North of the camera (the more the camera is tilted, the further North the centre of the screen will be), to which you would add your camera_floating_height constant.
Unit selection typically involves allowing the player to click on an individual unit or drag a rectangle around several. CameraPick solves both of these problems: finding the unit under the mouse or finding the start and end points for the rectangle on the terrain.