Here is a blog of one of my favourite practising Instructional Designers. Christy gives a really good overview of current ideas of theory and how they relate to the field. I think it is useful as the blog acts like a bridge between our course and the 'real-world.' It doesn't provide an-depth analysis of the job, but you can see how the process is informed by cognitive theory, behaviourism, and constructivism, and also follows Wilson et al's ideas of effective instruction.