I recently discovered the illustration blog Ape on the moon. This blog is a great resource for anyone interested in the art of illustration. The blog is run by two talented british illustrators, Alex Mathers and Philip Dennis.
Alex Mathes has written books about the commercial side of working with illustration. "The indispensable illustrator" is about how to get yourself noticed in the huge crowd of fellow illustrators. The other book, "How to get illustration clients", is a 100-page guide, as well as a full length audio with extra commentary and more resources. You can order the books through redlemonclub. I´m thinking of taking this course soon. I really think this could be useful to me. Verdict will follow in a while...