For those who like to write map-reduce programs in python, there are good toolkit available out there like mrjob and dumbo.
Internally, they still use Hadoop streaming to submit map-reduce jobs. These tools simplify the process of map-reduce job submission. My own experience with mrjob has been good so far. Installing and using mrjob is easy.
First ensure that you have installed a higher version of python than the default that comes with Linux (2.4.x for supporting yum). Ensure that you don't replace the existing python distribution as it breaks "yum".
Install mrjob on one of the machine in your Hadoop cluster. It is nicer to use virtualenv for creating isolated environment.
wget -O virtualenv.py http://bit.ly/virtualenv /usr/bin/python26 virtualenv.py pythonenv hadoopenv/bin/easy_install pip hadoopenv/bin/pip install mrjob