I stumbled across this blog post by Chris Beams, it has a very clear explanation of the way git expects commit messages to be formatted. Being able to place explanatory paragraphs, links, pasted error output etc really improves the history of my repos. It was always a struggle with CVS and SVN choosing between an extremely long commit message or losing context. The tools are able to distinguish the title from the description too and so can choose how and where to display them as appropriate.
Stuff about Programming
The Decimal class in the standard library is the way to avoid double precision errors in Python.