Cameraquest Classic Camera Articles: An amazing collection of rare cameras.
Film Photography Project: The cheapest place to buy film (even internationally), as well as the best film podcast.
Ken Rockwell: In depth reviews of cameras, lenses and gear, old and new. Mostly focused on digital photography, but Ken's articles on film are informative.
Camera-Wiki: The camera wiki. Splintered after the Wikia takeover. Somewhat mothballed, but still some good information here.
Massive Developing Chart: The go-to resource for developing your own film at home. Pushing, pulling, stand-developing, cross processing, dilution calculator etc. Contains development information for almost every film stock ever made.
Fred Parker's Ultimate Exposure Computer: How to use your brain as a light meter.
Emulsive: Open submission film photography articles. Everything from camera reviews, philosophy and darkroom tips. Also home to the Emulsive Secret Santa event, a film photography gift exchange I've participated in.
35mmc: Very similar site to Emulsive, but focused 35mm rangefinders, compacts and lenses. Mostly film, but has the occasional article on digital photography.
Leica Cameras Used by NASA: The Hasselblad was ultimately chosen to be the camera to go to the moon, but Leica did attempt to compete, developing this super interesting prototype for use with space suits.
Night Fly Photography: Wide field astrophotographer who takes breathtaking large format images of the stars.
Frankencamera: Interesting projects to build digital backs for film cameras, including the Leica M3.
Canon Range Finder: Excellent historical and technical information about the development of early Canon rangefinder cameras. Well sourced, with incredible images of pre-war camera development. Also of interest are some of the more unique M39 Lenses.
Malaysian Internet Resources - Photography: Thousands of high quality images, unrivaled information and sources related to classic photographic gear of all types - a total rabbit hole for camera fans. Particularly dense are the articles on early rangefinder lenses.
Leica Lenses for Normal People: Clear, honest reviews of L39 and M-mount lenses, divorced of marketing nonsense. Does it have a soul?
Refracted: Personal site of John Marriage. Cool articles on photohistory and oddball photo techniques.
Ihagee.org: Website of Hugo Ruys, the definitive collector of Ihagee cameras, lenses and related material. Quintessential old school camera site.
NASA Innovative Advanced Concepts (Wikipedia has a more legible list layout): NASA's studies on the science and technology of the far future. I recommend reading the articles on non-rocket launched spaceflight, especially momentum exchange tethers. Formerly known as The NASA Institute for Advanced Concepts.
ABM 101 - The Restless Technophile: Fascinating writeup on ballistic missile defense and the countermeasures devised by missile designers to counter anti-ballistic missile systems.
Dressing for Altitude: U.S. Aviation Pressure Suits (NASA) by Dennis R. Jenkins (PDF): The pictures in this book are incredible. I would love to own the hardcopy.
Covert Shores - H.I. Sutton: Definitive source for narco-subs and other spooky seafarers on the web.
U-boat.net: Tons of information on the Battle of the Atlantic, both during WWII and WWI. Includes individual ship records, with a special focus on submariners.
Finnish Wartime Photograph Archive: Images of the Finnish Wartime experience, 1939-1945. Available in English. A shining beacon as to how a archival digitization project should be handled.
Imperial War Museum Digital Collection: Intuitive and searchable digital archive with an impressive number of photographs. Most interestingly, a solid number of 3D objects have been included in the digitization program.
National Archives and Records Administration: Online portion of NARA. It should be noted that the National Archives only holds records of government agencies, with a few exceptions. Anyone can request any files they have on hand via email. It's free to ask for digital scans of documents under 30 pages. Physical copies and bulk scans cost money though.
bellin¿cat: Someone is always watching.
Fantastic-Plastic: Plastic models of rare and exotic aircraft.
Old QSL Cards: Archive of old QSL (radio) calling cards, and the stories of their creators.
Simmon Menner's Stasi Collection: Selected images from the archives of notorious East German security agency, by artist Simmon Menner. These images are amazing. He also runs a fascinating blog. (CW for the other material on his site: Some scenes of extreme violence and gore. Doesn't apply to the Stasi Archive.)
War Bird Photography: Collection of historical images of German, Japanese, Russian, French and Italian Second World War aircraft.
Dave's Warbirds: Impressive collection of aircraft schematics and other information.
Luft46: Blueprints, models and design documents of Nazi Germany's influential and often bizarre aircraft prototypes.
Never Was: Alternative history magazine with indepth articles about diselpunk, steampunk, tropes, etc. Lots of really interesting materials and images make for great worldbuilding inspiration.
Bilingual Manga: Scanned manga in both English and Japanese. A fun way to practice comprehension.
Steven Kraft's Japanese Projects: Tons of really useful drilling programs for conjugation.
NHK NEWS WEB EASY: Japanese language news in simple to understand sentences. Includes furigana for the more intense kanji. In conjunction with a program like Rikai-kun, it is a great way to learn new vocabulary.
Wanikani: Save me from this hell.
aggie.io: Draw with your friends!
DDR-Navi: List of all the current DDR cabinets in Japan, organized by region/prefecture.
Zenius-I-Vanisher: Bemani forum with a good list of current DDR cabinets outside of Japan.
playingCards.io: No nonsense virtual tabletop.
JSpaint: A great browser based replacement for the old MS Paint app.
Ascii Paint: Fun tool for painting with ASCII characters.
unsplash: Royalty free images.
ascii.co.uk: ASCII art collection and generator.
cooltext.com Stream: A realtime(?) stream of all of the text being rendered on cooltext.
SaltyBet: Two to four modded MUGEN fighters compete in a best of 3 deathmatch. Viewers bet fake internet money on who will win. Makes a great drinking game.
SpriteClub: A lower population version of SaltyBet? I like their giant, accessible character list.
irasutoya: Ubiquitous Japanese clipart. Has an image for any situation you could possibly think of.
Listen.moe: Anime/J-Pop internet radio. Also has a K-Pop station.
r/a/dio: Anime music internet radio station run by /a/.
patlabor.info: Comprehensive Patlabor fansite.
Zimmerit.moe: Beautifully written and well researched blog devoted to 80s anime. The focus here is on mecha, but other content is spread throughout.