Those of you that have taken part in lectures on KGS will be familiar with Guo Juan and her online go school. I visited her site recently and discovered that she offers audio lessons there as well as at a separate address, audiogolessons.com. Unlike personal, one-on-one lessons which can costs a fortune, these lessons cost only one Euro. As of today, after the conversion, that doesn't even make it to $1.50 a lesson. Very affordable. From the information on the website, each lesson is available for one month after purchase.
-A Step By Step Course
In addition, the website also offers a few free lectures as well. Stop by her site.
For comments on the site: Sensei's Library-Audio Go Lessons