Museum voor Schone Kunsten, Gent/Museum of Fine Arts, Ghent
This painting always fascinated me since I was a child. It's a masterpiece of grotesque and horror vacui. And Bosch is tops on my list of favorite artists.
Two other versions are attributed to Bosch. Scholars differ on the date(s) of this version.
The Royal Library, Windsor Castle
Leonardo da Vinci's 'Study of Five Grotesque Heads' was done roughly around the same time.
The J. Paul Getty Museum, Los Angeles
James Ensor's 'Christ's Entry into Brussels in 1889' (1888) comes to mind. There are also affinities in the oeuvre of Otto Dix - another favorite artist - and George Grosz.
There are quite a few good books on Bosch, but most are out of print. Larry Silver's 'Hieronymus Bosch' (Abbeville Press, 2006) is a recent one, scholarly with copious and clean reproductions. I'm trying to get hold of a mint copy of Jos Koldeweij/Paul Vandenbroeck's 'Hieronymus Bosch: The Complete Paintings and Drawings' (Abrams, 2001). I didn't jump on it when it first came out. If you or someone you know have it, you're always welcome to donate it to me ;).