Just came across this handy MovableType plugin: MT-RSSFEED.
It can take any RSS feed (static file, or URL), and parse it for display within a MovableType weblog. I’ve changed over the RSS subscriptions to CAREO on the right sidebar to use this plugin, and it works pretty well.
There are lots more great MT plugins at the MT-Plugins Directory.
UPDATE: I’ve also put the “other” way of subscribing to RSS feeds in a page here, since it’s valuable in contexts outside of MovableType (like, say, Blackboard, or WebCT, or whatever…)