Readers Guide 

News and Reviews
Amazon.com - includes synopses, reviews, interviews, etc.
Beatrice.com - "...delivers daily literary news with an even tone and an open mind" -- NYTBR
BookBrowse - carefully selects from the most interesting current books and provides you with multiple reviews and a substantial excerpt of each
Booklist Magazine - includes reviews 
Bookloons - features, reviews and excerpts in many genres
BookPage - includes reviews 
Bookreporter - great interviews, book reviews,  and trivia for readers. You can even subscribe to their free newsletter!
Book Spot - comprehensive list of book-related resources on the web
Chapter One - featuring full first chapters of books with reviews and discussions, from the Washington Post
Complete Review - a "Literary Saloon" that reviews new and old books
London Review of Books
MoorishGirl - a blog featuring opinionated reviews of fiction and non-ficiton titles
The New York Review of Books
New York Times Book Review
USA Today Book Index

Awards
AwardWeb - indexed lists of Hugo, Nebula, Stoker and Aurora nominees and award winners, with links to other literary award sites. 
Bookawards - information about children's and adult literary prizes

Reading Groups
Ballantine Reader's Circle
Barnes and Noble Book Club - free monthly online courses about one contemporary and one classic novel
BookClubReader -a site devoted to providing book clubs with the information they need
Great Books Foundation - a formal approach to "great books" discussion
Harper Collins Reader Resources: Reader's Guides - reading guides include author information, interviews and discussion questions
Knopf's Reading Group Guides
Oprah Book Club
Overbooked - lists suggested books for discussion
Penguin Putnam - includes reading guides for classics
Random House Reading Group Guides - highly recommended publisher site
Reading Group Center - Vintage/Anchor Book's site offers reading guides, author interviews, prepublication alerts, tips for starting a bookclub, etc.
Time Warner Book Group

Reading Lists
Banned Books - the American Library Association's list of the 100 books challenged most often between 1990-2000
Bookbrowser - lists series and sequels
List of Lists - from Fiction-L, a Readers Advisory Listserv
What's Next? - adult fiction in series

Genre Fiction
Chicklitbooks - a guide to all things chick lit
Genreflecting  - a guide to reading interests in genre fiction
Focus Fiction - Read-a-Likes from the San Antonio Public Library
If you Like...A Handy Guide to Authors and Genres
Overbooked - Genre Fiction - links for ravenous readers; specializing in literary and genre fiction information
The Reader's Corner  - mystery, romance, fantasy

Mystery
ClueLass - includes mystery awards
MysteryGuide - reading lists for lots of mystery types
MysteryNet - online guide to everything mystery
The Mystery Reader - offers reviews of mystery novels
Poisoned Pen -  a mystery bookstore and more.... 

Romance
All About Romance - reviews and news of romance novels
The Romance Reader - features reviews, news, and articles about romance novels
Romantic Times - reviews and news about romance novels. Includes author biographies, writers' resources, and more.
Romance Reviews Today
Romance Writers of America

Science Fiction and Fantasy
FantasyFinder 
LOCUS online - newspaper of the science fiction, fantasy, and horror publishing fields
Recommended Fantasy Authors List
SF Site - with sample chapters, commentary, reviews, interviews, and more.

Horror
HorrorNet - resource for horror, suspense and dark fantasy fiction, including indexes for magazines, publishers, bookstores, reviews, author email addresses and author sites. 
Horrorfind
Horror Writers Association
Dark Echo Horror

Historical Fiction
Soon's Historical Fiction 
The Maiden's Crown
Prehistoric Fiction
Fictional Rome

Rare Books
Advanced Book Exchange - rare, used and out-of-print books
Atticus Used Books & Music

Miscellaneous
Cliff Notes
SparkNotes - similar to Cliffs Notes
Schwartz Books - visit your local bookseller online