Wikipedia: Amount of Substance
This Wikipedia discussion provides an extremely comprehensive review of the concept, Amount of Substance.
Technology UK: Amount of Substance
This resource, sponsored by Technology UK, presents an excellent overview of Amount of Substance and Mole, including explanations of relative atomic mass, relative formula mass and molar mass.
Nottingham Trent University: The mole misunderstood (PDF)
This excellent resource from Nottingham Trent University in the UK discusses why the concept of Mole is so difficult to teach and highlights common misconceptions held by both students and teachers.
MIT BLOSSOMS Lesson: How Big Is a Mole? Do We Really Comprehend Avogadro’s Number?
The magnitude of the number 6.02×1023 is challenging to imagine. The goal of this MIT BLOSSOMS lesson is for students to understand just how many particles Avogadro's Number truly represents, or, how big is a mole.
MIT BLOSSOMS Lesson: Stoichiometry
The aim of this MIT BLOSSOMS lesson is to relate the concepts of stoichiometry to daily life activities such as baking a cake, production of cars and the chemical reaction in the Haber Process to produce ammonia. The lesson seeks to enhance students’ problem-solving in stoichiometry involving the calculation of the masses of other reactants consumed and other products formed with the aid of a balanced chemical equation, given the mass of a reactant or product in a chemical reaction.