Great answers. The research definitely suggests that are many different types of stretching exercises that can improve ROM about a given joint.
Joanne describes the 4 most commmonly used types. Yoga, Pilates, etc. employ one of more of these fout types.
One point the research clearly supports is that to improve ROM, stretch following a cardiovascular or strenght workout when the tempurature in the area of the targeted connective tissues will be slightly elevated.