Sheffield University/Open University Java Applets.
These applets can be used to explore some of the ideas in the course. In particular, see "Powers of Permutations", "Permutations: the symmetric group S4", "Cosets, Lagrange and Factor Groups", and "Symmetries of the Square".
If you have any thoughts/comments about these, please let me know (or contact the authors directly: the email address is on the page).