Steve House has written an excellent article on connecting Flex 2's Tree component with a CFC back end:

What I find most interesting is how he handles returning a null value to Flex to handle cases where there are no children. This is definitely an article to bookmark. I'd love to see someone (Adobe? Me? Whomever) create a nice list of articles that are purely Flex+ColdFusion. Hey Steve - you mentioned you had trouble posting the article with WordPress. Maybe it's time for another blog? :)