Think Inside the Box
There is nothing that can give you a better idea of what makes a great ad than great ads, themselves. That's why I continually encourage you to immerse yourselves in the annuals.
That said, with the holidays coming up, I'd like to recommend a little inspiration. Pick up a copy of Ernie Schenck's The Houdini Solution. His basic premise is that thinking "outside the box" doesn't get you anywhere. You have to think inside the box - work creatively within the parameters you're given. That's where the real powerful ideas happen, because that's where they become relevant.
Chapter 10 is a list of 50 different ways to jumpstart your creative thinking. I think you'll all find them useful when you're coming up with your own ideas.