Photophool has a great CCRRFD-RNX Magnum DIY macro lighting solution using a cup... Thanks Steve!
After quite a bit of real world usage, I've concluded that most users of the Raynox DCR-250 aux close-up lens will be well served by this simplified version of my styrofoam cup ringflash emulator. The stronger 32 ounce cup makes it sturdy. The use of a single cup makes it easy to construct. Using velcro dots to attach the contraption to the Raynox universal clip-on mount makes it easy to change and provides a break-away connection to keep the cup itself from breaking if you hit it on something.
http://blog.makezine.com/archive/2008/04/diy_macro_lighting_using.html