Bibliographical
TolkienBooks.net – A comprehensive bibliography of Tolkien’s British publications.
The U.S. Tolkien Guide – A descriptive bibliography of Tolkien’s American publications including an extensive ‘Reference & Criticism‘ section.
Tolkien Collector’s Guide – Includes a discussion forum geared towards the Tolkien collector and numerous Tolkien-related bibliographic entries and articles.
The Compleat Gyde to Tolkien Calendars – A thorough illustrated guide for Tolkien calendars.
Wayne & Christina – The website of leading Tolkien scholars Wayne G. Hammond and Christina Scull. Includes a bibliography and useful ‘Addenda & Corrigenda‘ for many of their publications.
Online Stores
Tolkien Books – An eBay store dedicated to rare and collectible Tolkien books (run by myself).
The Tolkien Bookshelf – A Tolkien web 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 Publishers – 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.
Shelley and Son Books – An online bookstore with a focus on the Inklings.
Other
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.
The Tolkien Society – A prominent organization ‘devoted to promoting the life and works of J.R.R. Tolkien’. Publications include Amon Hen and Mallorn.
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.
[The] Silmarillion; book-collecting minutiae – Articles and digressions on book
collecting and Tolkien (The Silmarillion in particular).