SLIK2
If you want to light a 3d model then SLIK2 is for you. encompassing a full lighting system for the cg artist, SLIK2 can provide a complete lighting solution to light your models. Users can use the enclosed lighting setups, create their own or just as easily save out a customized HDR image to use for image based lighting. All of this can be done in the viewport and interactively using Preview. Nothing comes close to this type of streamlined workflow for realistic lighting solutions. While spherical maps are great for quick & dirty setups, SLIK2 offers real world lighting nuances that accentuate your creations.
SLIK2 is available free. You may use it for commercial and non-commercial projects. You may not however redistribute it. Thanks for all the support over the years to the wonderful 3d community.