The Centre for Education in Mathematics and Computing
This is a great site an educator could use for discussion prompts to promote critical thinking in the math classroom.
For Common Core resources, teacher videos, strategies and lesson plans, go to Teaching Channel. Find great ideas and strategies in classroom teaching videos covering Math, Science, English, History and more.
Here are some great simulation options for (mainly) math and science lessons by age level. Students will enjoy the hands-on, cause and effect manipulation offered by these activities.