Polygons

Regular and Irregular Polygons

 * Coolmath.com: [|Properties of Polygons]
 * Illuminations: [|Shape Tool]--Build any shape you want!
 * Math Open Reference: [|Regular Polygon]--a definition and examples of regular polygons
 * Totally Tesselated: [|Regular Polygons]

Special Properties of Triangles and Quadrilaterals

 * Mathwarehouse.com: [|Triangles]--Angles, Sides, Properties, and Rules
 * Maths.com: [|Quadrilaterals]--Learn about the properties of triangles.
 * [|Shapes: Triangles]--Learn about the properties of triangles.

Angles

 * [|Angles]: Learn how to measure an angle, classify angles, and other angle properties.
 * Coolmath.com: [|Sums of Interior Angles of Polygons]
 * Illuminations: [|Exploring Angle Sums]
 * Math.com: [|Classifying Angles]
 * Mathsisfun.com: [|Shapes, Space, and Measure]--Learn about how to measure angles.

Tiling

 * [|Mathnet: Transformational Geometry]--Symmetry, Reflections, Rotations, and Translations
 * Totally Tesselated: [|Tilings of Regular Polygons]

The Triangle Inequality

 * Key Math: [|Exploring the Triangle Inequality]
 * Online Math Learning.com: [|Triangle Inequality]

Pythagorean Theorem

 * [|Animated Proof of the Pythagorean Theorem]
 * [|Interactivate: Pythagorean Explorer]
 * [|Interactivate: Squaring the Triangle]
 * [|Math.com: Right Triangle Facts]
 * [|Math Forum: Proof of the Pythagorean Theorem]
 * [|NCTM Illuminations: Proof of Pythagorean Theorem without Words]
 * [|Pythagorean Theorem Web Quest]

Finding Distance & Length of Line Segment

 * [|Regents Math: Distance of Line Segment]
 * [|SLU Mathematics Tutorial: Distance Formula]

Mixed Resources

 * Mathsisfun: [|Plane Geometry]--Resources about polygons, angles, and transformations.