CutTheKnot: A Puzzle on the Petersen
Illuminations: Vertex Edge Graph Creator (flash)
MathIsFun: Four Color Theorem
MathIsFun: The Seven Bridges of Königsberg
MathIsFun: Euler's Formula
The Poor Cartographer
MathWire: Map Coloring
The Young Map Colorer
Lumen: Euler and Hamiltonian Paths and Circuits
Vertex Edge Graphs
NRICH: The Four Colour Theorem
JDHamkins: Graph Coloring
GeeksForGeeks: Walks, Trails, Paths, Cycles and Circuits in Graph
Paths and Circuits