I had a great time with my coworkers in St. Louis at the NCTM conference. I went to talks on assessment, questioning, struggling learners, fun math, challenging brain stretchers .... I'm revitalized to end our school year.
Here's one puzzle I got from a presenter. She puts up a new line every day, and her students have to guess the pattern (and/or guess the next row of numbers). I'll put up a few, but of course it goes up in stages and can go on forever (and lead to interesting follow up questions).