Fawn Nguyen's Visual Patterns site so useful at helping students understand the connection between pictures (the pattern), numbers (table of values), symbols (algebraic representation), and words (the description of the connection between the representations).
Khan Academy is a free resource that provides videos, instructions, and activities. You can use their resources in your classroom lessons.
Open Middle is a website that offers math problems for grade levels K-HS. You can use it as a database.
Robert Kaplinsky compiled great problem solving activities for Math. They are often accompanied with files of videos and images to assist in building your lessons. Sorted by grade level, you can choose which activities you are interested in, select and download the activity. You can view the "How tall is Mini-Me?" activity I created from a Kaplinsky download.
Annenberg Learner is a website recommended by the Marzano ASOT trainers. You can search the Lesson Plans or Interactives tab and find many activities that you can use in your classroom.
NeoK12 is a website that will help you search for videos, games, and lessons that you can add to your classroom. It does contain many of the education videos found on YouTube, so it can save you time filtering through them.
Would You Rather is a website that collects great problem solving situations that encourages critical thinking. With a category listing on the right, you can easily search for problems to add to your activities. Take a look at the four examples below.
Prodigy is a free math game that the students love. I covers content from K-8 grade. You can assign specific TEKS to be covered on certain days or just let the program spiral material based upon the assigned grade level. Chromebooks can link to the website through an app from the web store and Ipads have a downloadable app from the Itunes store.
CosmoLearning has entire lectures available for sharing with your students. Though most of the material is high school and college level, they do have some materials for the lower grades.
Visnos provides visual math demonstration activities. Their activities are interactive and engaging. They are also continually adding new content to this beta site.
Fog Stone Isle is game focused on fractions. Starting with activities that require addition and comparison of fractions, it quickly moved to multiplication of fractions and mixed numbers.
Funmaths.com provides resources for high school teachers - worksheets, lesson plans, fun ideas, games and puzzles covering all the advanced topics like algebra, trigonometry, calculus, statistics, geometry and more.
You will find printable math worksheets, tutorials and math review , cool math games, math puzzles and all sorts of fun math projects for high school math students.
Thatquiz is a great tool that I have used many times for self-grading practice. I generally select 10 problems, then if they score well, they can move on to another activity. If they are struggling, then I would reteach and then have them try a new set of 10. This is a great way to quickly allow students who have mastered the concept to move on to extension activities while quickly discovering who needs remediation. The video shows a high school level situation, but Thatquiz actually begins with basic single digit addition, so it is appropriate for all grade levels.
Math Pickle is a great tool for finding extentsion activities. Sorted by grade level, you can easily find activities for your classroom.
Hooda Math is a collection of online games that is sorted by grade and category. The students can go online and play on their own or you can create a class and organize a set of games that you want them to work with. When you set up your own class, you will be given a class code that the students will use to "unlock" the activities you have selected for them. I do recommend this so you can filter through which games your students will need.
Follow this link for a growing list of great online Math Resources