According to this blog sumarizing research findings, they can! Glaciers are effecting the amount of gravity in certain areas of Canada. I doubt you'll be able to go up north to the area in question and bounce around like you're on the moon though, but it would be interesting if a local student did a Science project about the graviational force in that region. It would consist of someone timing how long it takes for an object to fall and compare it to other parts of the Earth. (Hey! It could be a project with participants from all over the world! ....hummm that's a thought, it would be perfect for 8th graders)
Link: http://www.livescience.com/environment/070510_odd_gravity.html