Best way would be to write a plugin that listens for the hook action:user.create. This hook receives the userData and is fired whenever a new user is created.
Is there anyway to extend the "topic" api to return both the first post teaser/user AND the last post teaser/user? Currently, its one or the other in settings.
Actually, to my knowledge, we don't really have a category that shows all posts from all categories... maybe /recent, but we'll have to take a look at your site to see what you're talking about!
