Simon Fell > Its just code > Tackback OPML
I ran with Sam's idea and put up a modified version of the OPML directory browser that supports trackback. Send a trackback with just a title to add a new folder node, send a trackback with a title and link to add a link. If the link ends in .opml, then it inserts the linked tree at that leaf. An OPML doc of the additions is available. Source code is also available.