Having to drive 30 minutes each way to find an actual hill ... I agree with this totally - If I was training for a 100 with any hills, I would drive out twice a week.

+1 to "stairs of death" but +100 to the actual hills.

My 7 favorite cross training activities:  Racquetball, Volleyball, Downhill skiing, cross country skiing, snow shoeing, biking and Wakeboarding.   There is a certain core building activity I like a lot also ...

Volleyball, Racquetball and Downhill skiing are great quad workouts.

I'm not big on cross-training.  Exercise machines, weights, and anything that has me standing in the same spot while I exercise is dull and tedious to me.  I consider parts of my daily life to be cross-training.  Shoveling snow in winter, mowing the lawn in summer, lifting 50 lb sacks of chicken food, moving bales of straw, lifting groceries (you can do repeats as you walk from the car to the house) biking to work, lifting the baby (also can do repeats), playing with the dog, gardening, and doing cleaning, maintenance, and improvements on the house and yard are all ways that I cross-train.