I've noticed a need for basic stretching exercises and Bob Anderson's book on "Stretching" is a good book for the general public. He teaches about how to move into stretches gently without force. He also talks about a point where the stretch can back fire. There are sections for diff. types of athletes.
However, for those wanting to move into splits of all kinds and extreme backbends, I highly recommend that a proper teacher/coach be sought ought. There are certain stretching movements that can be harmful for the low back area if done improperly.
(finalyear, this would be a good resource for you also. )