The HappyLight Compact Energy Lamp is one of the cheaper SAD lights on the market, but is made by the reliable chaps (and chapesses) at Verilux. It only provides 2,500 lux of light, but is compact and portable and the light tone is lovely.
This Verilux HappyLight offers a variety of light intensities up to a maximum of 7,500 lux and is small and weighs next to nothing. It is also made by Verilux who have a strong brand name when it comes to SAD lights.