Bamboo straightens easily with heat. Just carefully heat the spot you want to straighten until it starts to "sweat", at which point it becomes plastic. I like to do the sections between nodes first, then straighten the nodes themselves. Be sure to let the spot you were bending cool down before straightening another section of the same shaft, or it will keep bending as you work the other spot.
Bamboo arrows are hard to beat for hunting, and work great with stone tips.