Jump everywhere = Athletics to 100.
Well, the jumping actually levels up Acrobatics. Just running around increases Athletics. [/smartass]
Fun tip: If you fall a longer distance onto the ground, you level up Acrobatics more. So if you jump down a mountain, you'll get a lot more experience than if you jump off a short rock.
Just make sure you have the health and healing potions to survive the fall and patch up.
If you need any help, I probably remember 99% of all the quests and miscellaneous stuff. My mind is full of useful video game information.