A mining pool.
This pool pays out using a proportional share reward system (your shares / total shares for the round) = % share of the rewards. There is also an optional pay per share.
The service was first available on May 17, 2011.
PPS was discontinued on June 21, 2011 . Pay per share fee was 5%.
- Proportional: 0% fee.
See Also on BitcoinWiki
- Continuum web site