Home improvement stores have tubing for that purpose. It's flexable and opens along the length so you just lay the wires inside and the tube closes back up.
Buy and fix a clip on plastic track for hiding wires available at DIY's.
They have some great cord gathering gadgets on Amazon. One I bought was fabric. You could use the white side or reverse and use the black side. You could cut the length and it was Velcro so cords could enter and exit at different places. It was awesome!
You can purchase wire covers that can be painted to match the wall. You run the wires inside them.