Plickers is an easy-to-use website/app to do multiple choice review problems in class. All you need is an internet-connected computer, a projector to show the students the questions, and a smartphone with the app. The students hold up answer cards, and you scan their answers with your phone's camera. It works very smoothly!
Harvey Mudd College's math department puts up math fun facts. It is full of really neat stuff! This recommendation was passed on to me by Marc Rios.