This online textbook and interactive provide a foundation for introductory coursework on probability and statistics.  Lessons pertaining to probability are included in Chapter 1, 2, and 3: Counting Methods, Calculating Probabilities, Expected Values and Simulations.  The Flexbook can be read online or downloaded in .PDF format.

Cut-the-Knot.org provides in-depth high-level explanations of probability theory, puzzles and problems.  These include discussions of intuitive probability, conditional probability, binomial distribution, geometric probability, Sicherman Dice, Bayes’ Theorem, dependent and independent events, random walks, and probability paradoxes.

Is your ability to guess the total when you roll the dice based just on chance or is there some probability of how frequently you will roll different numbers?  See how increasing and decreasing the number of dice rolls affects the likelihood of a given outcome.  There is an accompanying explanation for the results of the histogram.

There are five games of probability.  Each has an accompanying background and explanation for how to estimate the probability of winning them.  There are two coin games, a dice game, a pick-the-winning-key game, and the “Monty Hall” puzzle pick-the-door game.  All the games show historical and expected results, and you choose how many times to play them. 

These two probability interactives with accompanying worksheets are designed for students in grades 6-8.  In the first activity, Toads and Vines, students explore outcomes from rolling a die, tossing a coin and using a spinner to perform single and double event probabilities.  Prinouts include other activities, solutions, a board game and learning strategies.

In the second activity, kids compare theoretical and experimental probabilities, and the Monte Carlo Method.  A video illustrates how this math is used to evaluate risks and the danger of avalanches in the mountains of Alberta.  In the interactive, students operate a simulation of 6 downhill ski runs.  The accompanying printouts help them practice the math to determine  and extrapolate these probabilities.