Using natural light
Using a large window is a fantastic way of using natural light and net curtains are an excellent way to diffuse natural light making it less harsh, much the same way as a softbox works with studio lighting. A silver reflector will also help bounce the light back to the shadow side of the face.
Natural lighting is all around us and is completely free, there are however some draw backs to it, that being that we cannot control it like studio lighting, and on dull days or in low light you need to work with higher ISOs which start causing graininess.
Alfred Stieglitz, Sun rays image entitled - Paula 1889 scanned from Richter PC, Prestel Georgia O'Keeffe and Alfred Stieglitz 2006