In the interest of people using SO as a research resource/tool it would be good to be able to mark questions as "unread" instead of just star them. That way you can work through your list of "unread" questions in order to learn about certain topics you are interested in marking them as read when you're done. Stared questions are more useful for questions you really like and want to keep an eye on.
E.g. "I have no time ATM but a question I came across looks really interesting and I want to save it for future research."