If it's of use to anyone, I wrote this fairly thick-headed script to look for the most recent versions of files matching one or more patterns in a directory, zip them up and back them up to Amazon's S3 Service using boto. It also deletes all files in the directory that are older than a given number of days (unless the file is being backed up in the current run). Even includes a bit of progress feedback, though nothing fancy.
The script is designed to be a Django management command because I'm lazy and like to keep all site-related files under Django, but there's not much coupling: just define your keys and patterns in the file, get rid of the Django "class Command" stuff and turn it into a normal script if you like (you'll have to find a new way to send email notifications on error if you do).
It ain't pretty and the parameter handling is crap, but it's a start.←