Crime Thru Time Lots of book lists, brief but helpful reviews, and a listing of new/forthcoming releases are featured here. Also note the very useful Timeline, which arranges books by the era in which they take place.
Euro Crime A site for fans of British and European crime fiction
Hardboiled Heaven For those who enjoy walking the "mean streets" of the genre.
Historical Mysteries Extensive lists of historical mysteries are arranged by both author and time period.
I Love A Mystery Formerly a print newsletter, I Love A Mystery is now online. Browse their collection of reviews by reviewer's name or go to the table of contents for books listed alphabetically by title.
In Reference to Murder Organized links to every imaginable topic of interest to the mystery reader
Killer Books Monthly reviews of books you might have missed, provided by the members of the Independent Mystery Booksellers' Association.
Looking for a Mystery? "Look for a Mystery by Date" highlights major mystery writers of each era; "other Places to Look" provides links to mystery booklists on almost every conceivable topic.
Mysteries in Print Arranges book review by category: amateur sleuths, legal thrillers, private eyes, etc.
Mystery File A blog devoted to mystery and detective fiction; emphasis is on older titles
Mystery Ink This site includes recommendations and reviews, guides to authors, booklists, interviews, and a section on books made into movies.
The Mystery Reader Lots of reviews, arranged in categories like Thrillers, Historical Mysteries, and Cozies. Features include lists of forthcoming titles, mystery news, and introductions to new authors.