This article presents an effective course supplement for Principles of Marketing classes. An experiential project involving online auctions is offered to instructors seeking to create a more participatory student environment and an interactive teaching style. A number of learning points are illustrated that allow instructors to use an auction project to illustrate specific Principles of Marketing concepts as a living case study. Emphasis in the present context is given to the illustration of the marketing mix, consumer behavior, ethics, e-marketing, and marketing research topics. An example for more advanced purposes is also provided. (Contains 5 tables.)