I used my good old salad bowl (http://www.flickr.com/photos/nophotos77/2589 246961/) on the camera right top with a 430.
For the BG / backlight, I had mounted a 540ez with a snoot aimed at a thick black foam board. The board had a 30cm x 30cm square cut out which I had partially taped over with some card board stripes and a blue and green folder cover.
I could control the sharpness of the "rays" somewhat with the focal setting of the flash, but the angle of the flash to the wall wasn't very good (there was little space outside the frame).