For many years, educators have been discussing benefits of educational practices such as the use of real-world examples, visualisation, interactivity, constructivism, self-paced learning and self-paced testing. Macromedia Flash MX has been used to develop online modules for the course Differential Equations offered at the University of South Australia that utilize these practices. This paper demonstrates the following innovative features of the modules that provide an effective online learning environment: (1) graphs which allow the user to interactively vary parameters are accompanied by "walkthroughs" that break mathematical content into manageable chunks; (2) a clearly labelled navigational structure that implies a linear order for each module while allowing users to jump forwards or backwards; and (3) animations such as an oscillating spring which depict real-world examples. Online multiple-choice quizzes with randomized numeric values is a unique form of assessment that will be discussed. The integration of a wide range of effective learning principles into online modules will be the focus of this paper. (Contains 2 figures.)