I love these lessons/units. Hungry Teacher takes the regular teachings and adds some fun. What can you create?
http://hungryteacher.com/our-lessons/

The math of Connect Four explained.
http://www.dump.com/connectfour/

Some “Odd” Theorems
http://www.futilitycloset.com/2013/11/25/some-odd-theorems/
Draw any triangle and divide each leg into three equal segments. Connect each vertex to one of the trisection points on the opposite leg, as shown, and the triangle formed in the center will have 1/7 the area of the original triangle. A square inscribed in a semicircle has 2/5 the area of a square […]

Part 4: Math and Project Based Learning... 22 Amazing Resources http://wp.me/pBrsB-1ak Obviously, be sure to backread the first three parts!

On the Flying Colours Blog, my favorite post was probably The Geometry of Sec(x) - although I quite liked the Mathematical Ninja taking probability trees to pieces as well. He also had a neat mental arithmetic trick for S1, which I'm still learning to do quickly. (I tried today... and failed. Will do better next time!)

Mowing the Lawn – Three-Act Math Task goo.gl/NFtyHi

30 NCAA Basketball Lesson Links ... PBL Series... Best Classroom Lessons Never Taught http://wp.me/pBrsB-1dI

Math Magazine -
http://rmm.ludus-opuscula.org/