Transfer Old Posts to New Custom Post Type

Has anyone transfered old standard posts to a new custom post type? What would the best way of doing this?

Example: I have “sermon” posts that (prior to WordPress 3.0) lived in the normal “Posts” section of the admin. With WordPress 3.0 I created a custom post type for Sermons. How would I move all of the old sermon posts to this new custom post type?

Thanks in advance.