The syndication module organizes all the RSS feeds that a site produces into one page, making it easy for users to see all the feeds available to them.

A book is actually two separate things. One is a hierarchical structure or outline that can contain any other node type. So, for instance, you could add a blog entry, a story -- or even a weblink -- to a book outline. This is a good way to organize content (especially different kinds of content) without having to create yet another category. An example would be "Mexico 2004" -- you could tag all of the content you create (like blog posts, images, etc.) with a term like "Travel", and then order them all in your Mexico 2004 book (since you are unlikely to add to a category called Mexico 2004 in the future).