Authentic Parallel Structure for ESL Students (Great graphics to illustrate parallelism but sensitive content)
Empire State College's Writing Style Seminar, includes section on Parallelism.
Opera in Thorold (An online activity for ESL students but gives a good idea of an ESL approach to this. You might want to do project this and use it as an in-class activity)
Elements of Style (Strunk 1918 without White is apparently public domain and available to all over the Web)
Parallelism and online quizzes based on Strunk