Dan Meyer's Three-Act Math Tasks — This teacher use visuals to hook their kids and then has them search for the answer to the problem. Appropriate for 6-12 grades
EngageNY — may need to search for a specific task that will work, but there are a lot of options
Illuminations: Resources for teaching Math — This site has pre-created lessons delineated by grade level. You may have to search but there are some great ideas for anchor tasks! All grade levels
Illustrative Mathematics — Has limited resources, but they have performance tasks related to each CCSS
Ricky MIkelman's Singapore Math Binder — Click on "Anchor and Performance tasks in the black tabs to find teacher created anchor tasks for grades K-4, delineated by CCSS
Tasks: YouCubed at Stanford Univeristy — These tasks are created by YouCubed at Stanford University, they cover a range of topics and grade levels