See http://metric-fu.rubyforge.org/ for documentation, or the HISTORY file for a change log.

How to contribute:

1. Fork metric_fu on github.
2. 'gem install metric_fu --development'  #to get development dependencies
3. Run the tests ('rake')
4. Run metric_fu on itself ('rake metrics:all')
5. Make the changes you want and back them up with tests.
6. Make sure two important rake tests still run ('rake' and 'rake metrics:all')
7. Commit and send me a pull request with details as to what has been changed.

Extra Credit:  
1. Make sure your changes work in 1.8.7, Ruby Enterprise Edition, and 1.9.1 (Hint use 'rvm' to help install multiple rubies)
2. Post to the Google group explaining what you did and why you did it (I don't merge things in immediately so others might want to use what you've done). 
3. Update the documentation (web page inside the 'home_page' folder)
4. Update the History and give yourself credit.


The more of the above steps you do the easier it will be for me to merge in which will greatly increase you chances of getting your changes accepted.
If you want to do something really radical (which will touch over %30 of all the files) you might what to ask the Google group first to see if anyone is interested in your change before you spend a lot of time on it.

Resources:
Homepage: http://metric-fu.rubyforge.org/
Github: http://github.com/jscruggs/metric_fu
Google Group: http://groups.google.com/group/metric_fu
Issue Tracker: http://github.com/jscruggs/metric_fu/issues
My Blog: http://jakescruggs.blogspot.com/