I recommend the following sites and have found them useful in contextualizing different readings for students.

Perspectives in American Literature: An Ongoing Research and Reference Guide: http://www.paulreuben.website/pal

The Melville Society: http://melvillesociety.org/

Book Graphics: Rockwell Kent’s Illustrations for Moby-Dick: http://book-graphics.blogspot.com/2013/08/moby-dick-or-whale-illustrated-by.html

The Sublime: http://www.webpages.uidaho.edu/engl_258/Lecture%20Notes/sublime.htm