UPDATE 2/9/2021 – Since this post has collected more than 15 sites, I’ve created a Wakelet collection, which you can now find here.  The Wakelet collection will be updated with any future awesome math sites I find.

My students, especially my 4th and 5th graders, love math challenges.  If I can, I find ones that don’t show the answer so we can all try to figure them out.  I think it’s good for the students to see me struggling (and I really do!), and how I handle frustration over particularly devilish problems.  Last week, my 5th graders and I spent a good 30 minutes on this “easy” problem on Steve Miller’s Math Riddles page. (Technically, they had an excuse since they hadn’t exactly learned the math skill needed to solve the problem – yet.)

If you are looking for some unique math problems that will feel more like brainteasers than standardized test practice, here are some sites that I haven’t mentioned before:

• Steve Miller’s Math Riddles
• Plus Maths Puzzles Page
• Wild Maths (Click on Pathways at the top to get different puzzle categories.)

And here are some that bear repeating (*sites include activities for primary grades, K-2):

• Greg Tang Math Games
• Math Pickle*
• Mathigon
• Would You Rather Math
• Transum
• Math Monday
• SolveMe Mobiles
• Open Middle*
• Video Story Problems
• Erich’s Puzzle Palace
• Fido Puzzle UPDATE 2/9/2021 – This site is no longer available as it is Flash based, which is not supported 
• Which One Doesn’t Belong?*

With more and more articles coming out every day about the importance of modeling a good attitude toward math (like this one and this one), it seems kind of as simple as 1+1=2 to come to the conclusion that the people who have fun doing math will be more inclined to do it more often.

UPDATE 4/26/17 – I can’t believe I forgot to include this one: Estimation 180. So, there’s a bonus for you!

UPDATE 5/8/17 – I may have to change the title of this post soon because I keep finding more great sites!  Here is another one: Robert Kaplinsky’s Real World Problems.

UPDATE 10/19/20 – Try these Slow Reveal Math Graphs!