I like the BitCoin idea, mostly for the GPU computation part and to see if the idea actually holds. To get it running under Ubuntu 10.10 with NVIDIA CUDA 3.2 tools installed, requires some tricks as {{{python-pyopencl}}} requires a whole bunch of non-compatibele NVIDIA stuff to be installed.

  $ sudo apt-get install  blt dkms libboost-python1.42.0   python-dateutil python-decorator python-matplotlib python-matplotlib-data git-core libboost-python-dev
  $ mkdir ~/src
  $ cd ~/src
  $ git clone http://git.tiker.net/trees/pyopencl.git
  $ cd pyopencl
  $ ./configure.py
{{{$ cat <<EOF > siteconf.py
BOOST_INC_DIR = []
BOOST_LIB_DIR = []
BOOST_COMPILER = 'gcc43'
BOOST_PYTHON_LIBNAME = ['boost_python-py26']
USE_SHIPPED_BOOST = False
CL_TRACE = False
CL_ENABLE_GL = False
CL_ENABLE_DEVICE_FISSION = False
CL_INC_DIR = ['/usr/local/cuda/include']
CL_LIB_DIR = ['/usr/local/cuda/lib64']
CL_LIBNAME = ['OpenCL']
CXXFLAGS = []
LDFLAGS = []
EOF
}}}
  $ make
  $ sudo make install


Now download and run the miner. I run mine against the [http://eligius.st/wiki/index.php/Getting_Started Eligius Grid]. Replace {{{1AdxXkR3aB6xwPU6XwPZMZhu2v9avFuFoJ}}} with your own BitCoin Address, else thanks for the donation!
  $ cd ~/src
  $ git clone https://github.com/m0mchil/poclbm
  $ cd poclbm 
  $ python poclbm.py --device=0 --pass=x --host=mining.eligius.st --port=8337 --user=1AdxXkR3aB6xwPU6XwPZMZhu2v9avFuFoJ --verbose
 
For daily usage you can run it as a daemon with verbose logging if wanted:
  $ python poclbm.py --device=0 --pass=x --host=mining.eligius.st --port=8337 --user=1AdxXkR3aB6xwPU6XwPZMZhu2v9avFuFoJ --verbose >> bitcoin-mining.log &

If you have multiple GPUs in your system, make sure to fire up multiple installed with different {{{--device=}}} ID.