Originating from Penn state university this brochure details why food is iincreasing in price.
Several interesting stats here.
1. the USA has the cheapest food in the world
2. only .19 cents of every dollar actually makes it back to the farm gate
3. Wheat is currently (2005) 3.42 US a bushell. If wheat had kept pace with inflation it would be worth $16.21
4. US consumers can eat three servings of fruit and four sevings of vegetables for as little as .64 cents per day