Are cds marketed to help you sleep actually effective?

Some are: Most self help materials that you can buy easily from the bookstore may have a combination of passive muscle relaxation exercises and guided imagery techniques. These will most often help those folks that have a difficult time winding down physically and mentally. These are usually good for those that have brief periods of insomnia, and less helpful for chronic insomnia patients.

Personal preference: There are many available. It depends on you. Try one and see if it helps. Variable results.