Worksheets may be a "four-letter word" in the day of Common Core, but if you need some extra practice problems, this may be a useful math site for all grades 1-8.
Need some posters that explain the mathematical practices from the Common Core in terms the students can understand? This page has links to displays for grades K-7.
This is the PARCC page where you can click on links that take you to the actual online "live" samples of PARCC questions. You can click on math only questions for grade bands (3-5, 6-8, high school), or ELA only questions.
Need a great activity to get your students working on problems while moving about the room? This middle school math activity is explained in a short video, but while the topic is math, you can adapt the exercise to other topics too!