I've used colorful candies, number cubes (aka dice), spinners, random number generators and more to hammer the concept of probability into my students’ heads. Apparently not an easy idea to grasp for most people, otherwise Vegas would go broke. Technology can provide teachers with many of the manipulatives mentioned above and more to help students conquer this concept.
Undecided, published by Deadmans Productions LLC is a free app. It includes a dice roller, coin toss, spinner, drawing for the short straw, rock/paper/scissors, and a random number generator.
Dice, published by Benoit Layer is also a free app. It allows you to customize it to roll anywhere from one to twenty dice at a time. The total for the dice rolled is shown in the background. Settings include dice color, sound, and background.
Marbles Probability (Shodor)
This site simulates the random selection of from 1 to 3 marbles from a bag. The chart shows all possible combinations, the percentage that a theoretical likelihood of a combination will be drawn, and the experimental outcome as a percent of each combination.
Adjustable Spinner (Shodor)
The default spinner has four equal sections, but as the name implies, this can be adjusted. Just click and drag the slider next to each color, or type new percentages into the white boxes next to each.
Experimental Probability Spinner (Shodor)
As each color is spun, a tally is kept for each color. There are several pre-designed spinners or you can design your own spinner.
The Sum of Two Rolled Dice & Graphed Results (Saint Anne’s School)
This site will roll two six-sided dice and then graph the sum of the two dice. Click anywhere on the dice to begin, then press the space bar to roll the dice. The graph updates after each roll to reflect the sum of the two dice.
The Sum of Two Rolled Dice & Tallied Results (Shodor)
This site will roll two six-sided dice and tally the sum of the two dice in a chart. The dice rolls are displayed as a regular dice and as a net. You can also click the New Dice or Make Dice button to use a dice that repeats numbers.