The final set of lecture notes are posted -- they contain open problems. Some are definitely harder than others; some are definitely more interesting than others. If you have any more questions about them, feel free to comment. Also, if you are interested in working on any of them, let me know! If you are looking for an easyish-to-think-about problem, one that you can think about idly with a pen and paper while riding the bus, I might suggest the problem of extending the decision tree/influences inequality to real-valued functions.
I probably missed half a dozen better open problems out there. I may add to this list as they occur to me. To paraphrase Mitch Hedberg, these are the open problems I could think of today.