There are many commercial solar cookers on the market, some can even reach temperatures up to 400F (with the perfect conditions). However, it's easy enough to make one from common items.
The basic setup of a solar cooker requires a heat trap around a dark cooking container (with lid) and a reflector. The cooker should be aimed at the sun.
Go through the submenus in the DIY section to read about materials, set up, and samples of solar cookers you can make.