Tim suggested that I should have an RSS feed saying when my software releases happen; this could quite easily be done by just watching the listing of my files directory for changes. This could be generalised to produce an RSS feed that watched for changes in any web page, showing the changes in diff format.
There are sites around already that will mail you when a web page changes, but I'm not aware of any that do RSS. It'd be sort-of useful to support both; perhaps some generic Python module that accepted events, and either added them to an automatically-rotated RSS file, or mailed them somewhere. The first bit of functionality would certainly be generally useful.
Eliram Haklai pointed out that feed43.com seems to implement this now.