As far as working on your posture, you might want to check out the book 8 Steps to a Pain-Free Back by Esther Gokhale--it's all about good posture (the author did research in a bunch of different countries where people don't have the back problems etc. that we have here) and can help with more than just back pain. It doesn't address cycling but does address everyday posture when sitting, standing, walking and even sleeping.