This demo allows the user to visualize the integral of an arbitrary user-entered function. You can select the left hand, right hand, and trapezoid rules for integration. The integration step size can be varied, and the convergence properties of each method can be seen (i.e., generally linear for left/right hand rules, quadratic for the trapezoid rule). This demo is an excellent tool to visualize the actual process of Riemann integration, and would serve as an interactive teaching aid for an introductory calculus or numerical analysis course.