The authors describe a Web-based classroom experiment with two assets: cash and a stock that pays a random dividend. The interest rate on cash, coupled with a well-chosen final redemption value for the stock, induces a flat trajectory for the fundamental value of the stock. However, prices typically rise above this value during a session. The bubbles and crashes that occur in this experiment can stimulate a discussion of asset valuation, discounting, and pricing patterns that are determined by expectations and "animal spirits." (Contains 3 figures and 3 notes.)