Use a piece of plywood that fits behind your desk for a quick-fix solution for hiding cords that hang behind your desk. Measure the area beneath the desk and cut the plywood to a height that matches the desk. Sand and paint the plywood for a more finished look. Place the plywood piece behind the desk and make sure all cords go behind the wood. Attach it to the desk for added stability if desired.
Use cable management raceway to hide the cables on your desk. This product comes in a strip that you can cut down to the length you need. Make sure to use one that's thick enough to accommodate all your cords. Thread the cords through the plastic raceway. Remove the adhesive from the back and stick along the wall behind your desk or along the back end of your desk.
Install a hanging plastic basket on the bottom of your desk. Screw the basket into on the side closest to the nearest electrical outlet. Plug your power strip into the outlet and place into the plastic basket. Plug in all devices to the power strip and tuck the cords into the basket to hide them.