SU2KT is a Plugin for SketchUp.With it's help, you can export your models to Kerkythea and add Kerkythea lights and materials to SketchUp models. It can also be extremely useful when trying to export from sketchupa sit provides a method of producing an xml file that can then be converted to obj. It's a freeware, like Kerkythea. The latest release is 2.1. You could download it here until that link failed, kerkythea's website is currently down.