The Dante Lab
http://dantelab.dartmouth.edu/resources
This is an excellent and comprehensive online resource that also links to other online resources about Dante and the Commedia.
Divine Comedy: Purgatorio
by Dante Alighieri
Best summary PDF, themes, and quotes. More books than SparkNotes.
Divine Comedy: Purgatorio Questions and Answers
The Question and Answer section for Divine Comedy: Purgatorio is a great resource to ask questions, find answers, and discuss the novel.
