Many of us have used a sticker and other cheap solutions to cover our webcams in the past. If you are looking for a more elegant solution, you may want to give the SpySlide a look. It is 0.6mm thick and can be installed in a few seconds. You will be able to cover/uncover your webcam anytime you want.
The Spyslide is compatible with laptops, tablets, and all-in-one desktop computers. Expected to ship in May.