Biscuit Factory explores ratio relationships in the context of gears.
Biscuit factory: ratios
Biscuit factory: complex ratios
Biscuit factory: directions
Biscuit factory: create a two-gear system
Biscuit factory: create a three-gear system
Biscuit factory: gears and speed

Drive helps users solve proportional problems with distance and time.
Drive: hard problems

Squirt helps users explore and express proportional relationships.
Squirt: three containers: complex proportional relationships

NLVM: Number manipulatives
Sieve of Eratosthenes
Pascal's triangle

Learn Alberta: Exploring Number series.
Exploring order of operations
Exploring powers of 10

Learn Alberta: Exploring Fractions and Percentages series.
Exploring combined percentages

Learn Alberta: Exploring Measurement series.
Exploring ratios and proportions
Exploring square roots