Google maps for iPhone doesn't have contour/altitude lines.
I figure the squigglier the road the more it goes up.
Another recommendation for my mapping app of choice for the iPhone: MotionX gps
I'll second this. It's the only app on my iPhone I actually paid for and it was well worth it. Different tracking modes for cycling, running, driving, etc. Downloadable maps with good terrain coverage. Quite the deal.