We used to host some great middle school science projects on our roster. If you’re after an A+ science fair project, then one of the best resources you should check out is Janice VanCleave’s books. She offers the scoop on A+ Science Fair Projects and more. And if her style doesn’t suit, there’s always Science Fair Projects for Dummies (no offence!).
Search Sciencebase for science fair projects that can be done in 24 hours or over the weekend. There are also great ebooks out there such as ones with 101 science projects.