I've put up opmltools.zip - it's two scripts. One to backup stuff from your hosting.opml.org account, and the other to delete everything on your hosting.opml.org accont. Be sure to run the former before the latter. The backup script isn't particularly new or anything - coriHacks did it before me, but coriHacks can be a bit messy, since the OPML Editor may start trying to delete or upload your files. 
It's designed for Unix OSes (Linux, OS X etc.) and you need to have a reasonably recent version of Python (with xmlrpclib), and you need to have curl installed for backup (OS X has it). 
