TolkienBooks.net – A comprehensive bibliography of Tolkien’s British publications.
The Compleat Gyde to Tolkien Calendars – A thorough illustrated guide for Tolkien calendars.
The Tolkien Bookshelf – A dedicated online Tolkien store including first editions, signed copies, custom slipcases and plenty of other rare and hard-to-find items.
Houghton Mifflin Harcourt – Tolkien’s American publisher since 1938.
Random House – Tolkien’s American publisher for mass market paperbacks (including the imprints Ballantine Books and Del Rey Books).
HarperCollins – Tolkien’s publisher in the U.K.
AbeBooks – An online bookstore with thousands of new and used collectible Tolkien books for sale at all times.
Tolkien Estate – The official website for the Tolkien Estate. Includes articles on various topics written by leading Tolkien scholars.
Tolkien Gateway – An exhaustive Tolkien encyclopedia.
Beyond Bree – A monthly Tolkien publication containing news, articles and reviews since 1981.
Too Many Books and Never Enough – The weblog of Wayne G. Hammond and Christina Scull.
Tolkien Library – Articles, reviews and other helpful information for the Tolkien collector.