Reaper is a free and open-source OpenCL GPU miner for SolidCoin 2.0, coded by mtrlt.
Reaper has been successfully tested on both ATI and Nvidia GPUs. Although ATI GPUs appear to be more efficient, many types of GPU remain untested.
You may experiment with the software and try to attain the best hash rate you can and post your results on the official SolidCoin forum so you can be included in the Mining Hardware Performance page.
Besidess supporting GPU mining, Reaper can be configured to mine with the CPU too. Enabling CPU mining does not normally have an impact on GPU mining hash rates.
Detailed instructions on how to install and use the Reaper utility on your Mac are available HERE.