Slopes and gravity

Is there any simple way to keep a character from sliding down a hill due to the force from the gravity? I have tried turning the gravity off whenever the player came in contact with the ground, but I am having trouble trying to get it to re-activate when the character is no longer touching the ground. I can re-activate it when the player jumps, but that's not the only time the gravity is necessary, as the character can simply walk off a cliff, for instance, and not fall.

I know triggers have a onLeave function (or something like that) that runs when the objects no longer collide, but I was hoping to not have to use them. Is this the only way to really detect when they are not colliding?

Thanks.