Simple GPU miner with long pooling C++
This is the simplest miner I know of:


  pyminer
  
  This is a 'getwork' CPU mining client for bitcoin.
  
  It is pure-python, and therefore very, very slow.  The purpose is to
  provide a reference implementation of a miner, for study.


This doesn't support long polling, but there's a spec for that here.

:)