I'm tracking which miners made which blocks for a game that we built.  We decided to put the results of our block-watching on its own website and to provide an API.  Not sure if it's useful to anyone, but please check it out:

http://whomined.com

API:

http://api.whomined.com - return last 144 blocks (excluding most recent three)
http://api.whomined.com/#blocknum  - return 144 blocks from blocknum
http://api.whomined.com/miners - return miners statistic and misc info
http://api.whomined.com/miner//  returns last 144 blocks mined by miner staring with blocknum

Feedback welcome.  :-)