Here is the collection of book discussion resource links.

Deja.com
Popular online discussion destination for newsgroup readers. Contains thousands of new posts daily in hundreds of different categories.

eGroups Literature
Listings and links to different egroups for discussion of literature.

r/Books
A moderated subreddit dedicated to books, authors, genres and publishing.

Readers Read
Readers Read is a book blog covering the latest book news in all book categories.

SFF Net
SFF Net contains discussion forums and newsgroups about genre literature of all kinds.

Soapbox
BookWire's message boards for discussing books, literature and the publishing industry.