MathSite: An Interactive Source for Seeing, Hearing, Doing Mathematics is a collection of online, interactive mathematical games and activities that require no mathematical expertise for K-12 and older. Each activity includes a tutorial. The site requires Flash and Java and works best with an up-to-date browser, though for some activities alternative versions are provided.
Stable Marriage Problem is a classic matching problem. This interactive is a vastly simpler version of the National Resident Matching Program, which matches medical students with residency programs. The activity introduces the problem, matching four Kings and four Queens, and challenges players to make stable matches by trial and error, and then describes the Gale-Shapely Algorithm for making stable matches and challenges players to use it to make stable matches. Feedback is provided along the way.
Dissecting Triangles and Squares features a Polygon Dissection Gallery, a collection of eight activities, one of which explains how to cut any triangle into pieces that can be reassembled into a square and another describing the dissection of polygons with central symmetry.
Sorting Bricks and Sticks explores how to arrange things in order, the heaviest brick or the longest stick. Players use trial and error to determine an algorithm that will speed the process.
Geometric Orbits lets students experiment with geometric orbits on triangles, quadrilaterals, and pentagons.