archive.org – Almost every out-of-copyright book available here, in high-quality scans, usually in many formats.
Arts & Letters Daily – news and articles from the worlds of writing, art, philosophy, culture, academia etc
amasci.com – Bill Beaty’s unique and wonderful science site. Worthy of detailed exploration. Good on electricity, weird science, thinking about thinking etc etc.
SugarMegs – amazing bootlegs site. e.g. “Miles Davis 1971” turns up about 25 (!) whole concerts, free to listen online or download hehe. Heaven.
greatquotesonlifeandart.blogspot.com Quotes extracted from my diaries and notebooks, 1992-2003
The Wolfram Functions Site
Lang-8 – learn languages, write, correct and be corrected, make friends 🙂
SpanishDict – english/spanish dictionary, conjugation, translator
FICS (Free Internet Chess Server) is awesome. Started in 1995 when some people objected to the decision of ICS (now ICC) to start charging (a lot). Ad-free, monetization-free, run by volunteers. Old text-based software, but maybe the best online chess server. Download an interface at freechess.org, there are many to choose from. For Windows, Babaschess is unrivalled, a great pleasure to use. For Macs, Raptor and Jin are ok.
Chessbase – German chess news site
chess24 – chess news, videos, live games etc. New and shiny. Features the admirable commentaries of Jan Gustafsson.
The Chess Mind – Dennis Monokroussos’ chess blog, chess news and analysis with intelligence and wit. And high-quality reader comments.
Chess Notes – Edward Winter’s chess history site. For decades he’s been at work, almost single-handedly clearing the muck, innuendo, myth, exaggeration, lies, guesswork, laziness etc from the chess record. An inspiration and exemplar of historical patience, for every field, not only the chess world. Marvel as he exposes shady goings-on, huge effrontery, spineless copying, low exploitation, lazy vilification etc. A shining masterpiece.
Live Chess Ratings – Ratings of the top players updated constantly, with info on current and upcoming matches/tournaments.
Tim Krabbe’s amazing chess pages.
Sagar Shah’s chess blog
Also Chess.com has many great articles. Chess Cafe is now behind a paywall. Thousands of articles from the last few decades.