For really easy to digest research on Mathematics education from Cambridge Mathematics, see their Espresso page where in their words, “Each month we bring you an Espresso – a small but intense draught of filtered research on mathematics education, expressly designed with teachers in mind. Each Espresso considers one particular issue in mathematics education, and how the latest good-quality research can provide helpful guidance or further reading.”

Note the Research page which includes the link to this excellent site and more references whilst not specific to Mathematics I believe are important to teachers of any subject. Note the resources from Chris Moyse who understands that teachers are busy people!