Instead of just using Reading Lists to save, lets say a news article you were reading and couldn't finish, you can use Reading Lists as a way to temporarily bookmark a page without making a true bookmark. Since the Reading List feature just saves the link to the page it can be very useful.
An example is doing research and instead of making bookmarks and folders and what not holding the links to the research and then later having to delete it from your bookmarks just add the links to the Reading List. Since the links will remain in the reading list until you clear it out they won't be added to your bookmarks and when you're finish using them just clicking the 'x' on each one or clicking clear all will remove them, make it easier to manage links to pages for research and so on.
[crarko adds: This is one of those things that seems so obvious once you know about it, but is a little subtle if you don't. I have lots of unorganized bookmarks from old searches for projects and I'm going to try this idea in the future.]

