I have just finished my first cut at a csv file differ, pycsvdiff, written in Python. I decided to write my own differ, when, after a cursory glance around, I saw only two promising utilities. One was a cgi script that required uploading your files (not gonna happen!). The other was written in perl ('nuff said).
I have included a --run-tests option to verify things are working
The csv differ is built on top of more generic Table diffing code which is, in turn, built on top of even more generic sequence diffing code. I looked at SequenceMatcher in difflib, but this wasn't quite what I was looking for.
This was my first project written from the ground up using TDD. Needless to say, the ability to refactor with confidence was just, well, amazing! Not to mention the satisfaction that comes from the parade of dots that bolts across the screen. (dots FTW!). Now I wish I got one of those nosetests shirts at PyCon.