Real World Math: Concept Lessons - The Planes of Greenland
Real World Math

The primary goal of this lesson is to teach students how to use the Path tool in Google Earth. 

Real World Math: Exploratory Lessons - Four Color Map
Real World Math

This is a fairly simple puzzle for students to solve but it took over a century for it to be proven with computers. 

Real World Math: Exploratory Lessons - Network Theory
Real World Math

Network Theory investigations deal with how paths can be drawn in a continuous circuit.  

Illuminations: Pigging Out
Illuminations (National Council of Teachers of Mathematics)

This lesson uses the story of The Three Little Pigs to motivate students to think and reason mathematically in a number of ways.