Readers may find the Master and Margarita website[1] to be very thorough in providing the background information, plot and character summaries, and other supplementary materials. It is the best resource I know on the subject

There is also an active Bulgakov facebook page [2] with things like fan art and informations about upcoming adaptations.

As a matter of disclosure, I created the facebook page in 2008, but it has been run for many years now by Jan Vanhellemont, the man who is also responsible for [1]. I consider him to be the foremost fan of Master and Margarita on the English language internet.

[1] http://www.masterandmargarita.eu/en/ [2] https://www.facebook.com/m.a.bulgakov/