Illuminations

http://illuminations.nctm.org/

This website is full of great resources for teachers, students, parents, and anyone who is looking to teach or learn math.  Most importantly this is a very credible site as it was created by the NCTM.  Meaning all of the activities and lessons are designed around the National Math Standards. 

As a teacher I would use this site in my classroom for a variety of purposes.  Most importantly it's a great starting point to begin designing integrated lessons with specific connections to the standards.  There are over 600 lesson plans that have already been created for teachers to use in their classrooms. 

I would also use this website as a math center for my students.  Under the activities tab there are numerous interactive games that are specifically designed for students.  Again this is a great resource because each of these games are directly connected to a National Math Standards.  As a teacher you can even search games that are designed to focus on math content for each individual elementary grade level. 

Lastly, I LOVE the web links tab located on this site.  Because it is such a credible site itself you can be confident that the sites recommended under the web links tab on this page are also very credible useful math websites to use in your classroom.  Integrating technology in our classrooms has become a priority if we want to truly provide our students with the best possible learning environments.  This website is such a useful tool to help us do that and I would recommend it to any elementary math teacher!