You can now get a list of your RSS subscriptions in OPML format from the [[Topic Exchange]], if you’re using its subscription harmonizer service. The link is off the user subs page.

You need to be logged in (with a cookie) to see it, which means that can’t just pass the URL (http://topicexchange.com/user/subs/opml) into an aggregator to import everything, unfortunately. If you save the XML somewhere first, it should work fine, though. Suggestions are welcome for how to suitably protect a (possibly private) subscription list but still make it easy for people to hook everything together!