What follows is a highly recommended list of websites, in no special order, which provide a cornucopia of fun and information for Sherlockians. (Recommendations for additions are actively solicited!)
Sherlockian.net (https://www.sherlockian.net/) A huge list of links and home-based at the University of Michigan. One delightful Sherlockian nugget after another.
Sherlocktron (http://www.sherlocktron.com/) More good sources via multiple links. A treasure trove of interesting information for Sherlockians including a complete copy of The Canon.
Camden House (http://www.ignisart.com/camdenhouse/main.htm) A goldmine of resources including stories, graphics, audio, music, and more.
The Fortnightly Dispatch (https://www.youtube.com/results?search_query=fortnightly+dispatch) A delightful biweekly YouTube adventure featuring Stephen Doyle and marvelous guests from the Sherlockian community. Each program is under an hour. Extremely informative and addicting.
The Baker Street Irregulars & Baker Street Journal (https://bakerstreetirregulars.com/) The BSI home page which includes access to The Baker Street Journal and much more.
The Sherlock Holmes Society of London (https://www.sherlock-holmes.org.uk/) Excellent web site with numerous references (membership, newsletter, etc.) and archives.
The Best of Sherlock Holmes (http://www.bestofsherlock.com/) Lots of interesting info and fun for web-surfing Sherlockians including top-ten lists, manuscript details, and so much more about Sherlock Holmes.
Scuttlebutt from the Spermaceti Press (http://www.sherlocktron.com/scuttle.htm) A must read for all informed Sherlockians prepared by the great man himself, Peter Blau. Published monthly with copies available stretching back to 1985.
I Hear of Sherlock Everywhere (https://www.ihearofsherlock.com/) Another must for all Sherlockians to check out. Podcasts, special features, and lots more from Scott Monty.
The Canon of Sherlock Holmes (Wikipedia) (https://en.wikipedia.org/wiki/Canon_of_Sherlock_Holmes) A useful quick & dirty reference listing of Canonical and Noncanonical works by type, publication group, name, and date.
Sherlockian-Sherlock (http://www.sherlockian-sherlock.com/) An amazing English language website home-based in Hungary. An absolute treat for any Sherlockian to peruse.
Doyleockian (https://alistaird221b.blogspot.com/) A super neat and fascinating blog site with all sorts of interesting Sherlockian information and happenings courtesy of Alistair Duncan.
The Beacon Society (www.beaconsociety.com) A great Sherlockian organization which does lots of good work, especially relative to education-related support for both teachers and students. The place to go to encourage younger generation interest in Sherlock Holmes.
The Red Circle of Washington, DC (www.redcircledc.org) One of the oldest and leading scion societies in the USA. Great website and home base of Peter Blau. You can sign up here for Peter Blau's internationally famous (and free) Sherlockian newsletter, Scuttlebutt from the Spermaceti Press.
The Crew of the Barque Lone Star (https://www.dfw-sherlock.org) An outstanding scion society deep in the heart of Texas. First class website (contains the complete works of Sir Arthur Conan Doyle) and home base of Steve Mason, scion Third Mate (President) and superb Sherlockian cartoonist. Also publishes a great monthly newsletter (The Bilge Pump).
The Baker Street Babes (http://bakerstreetbabes.com/) Great ladies-only website.
The Adventuresses of Sherlock Holmes (https://ash-nyc.com/) ASH is the oldest women’s organization of its type which now also admits men by invitation-only. Excellent website.
Watson’s Tin Box (http://www.watsonstinbox.org/) Great Sherlockian scion website in Maryland.
Fevronia H. Watkins (https://www.patreon.com/TheAdventuresOf) Exciting new young female detective inspired by Sherlock Holmes. She lives on the Big Island of Hawaii in the late 19th Century.
221B Poem (https://juniorsherlockian.com/wp-content/uploads/2017/07/Studying-the-Poem-221B.pdf) Classic poem written by Vincent Starrett
Sherlockian Toasts (http://www.rossdavies.org/toasts) Terrific web site if you are in need of that special Canonical toast.
Pick-up Lines from Dr. Watson (Ten Pick-up Lines by Dr. John Watson (laughing-stalk.blogspot.com) A quick & fun read.