NASA
Nasa: Space Place: Messenger: Planet Mass Comparison
Compare the masses of planets in this interactive animation. Simply pile a number of Earths on one side of the scale, to balance with the mass of one Jupiter. Then try this with all the planets.
Curated OER
Exploratorium: Your Weight on Other Worlds
Want to lose weight in a hurry? Just step on a scale on almost any other planet! This page allows you to enter your weight on Earth and it will calculate your weight on all of the other planets, some moons and even some stars. Requires a...