Below are some resources I find useful.
Simply the best place to learn and discuss about GURPS. Think about it: a friendly community where you can have constructive conversations with next to zero trolling. I’ve been roaming the Net since 1997 and I can tell you, this is pretty unique!
GURPS Lite is the official light version of the core rules of GURPS: nearly 600 pages of material brought under 32 pages! Available for free at Steve Jackson Games.
MyGURPS is written by none other than Jason “PK” Levine, a prolific author for Steve Jackson Games. The website features articles, reviews, house rules and more. A must read.
A huge resource site for GURPS and RPGs in general, curated by TBone.
This is Douglas Cole’s blog. He’s been involved with GURPS for years and has authored many articles, as well as the famous GURPS Martial Arts: Technical Grappling.
This is Peter V. Dell’Orto’s blog. He’s also been involved with GURPS for many years and authored many articles as well as the hardback supplement GURPS Martial Arts.
Rob Conley shows us the way of old school roleplaying.
GURPS Character Sheet (GCS for short) is a utility written by Richard A. Wilkes. The program allows to easily create new characters for GURPS and relies on an extensible set of catalogues for determining the point costs of skills, advantages and disadvantages. Since it’s written in Java, you can run it on nearly any computer system.
Pizards has put together a great utility to get proper GURPS-compatible statistics for many, many animals. A lot of hard work, and one that can easily find its way into any campaign.
A rather old page where Incanus presents a fairly large compilation of house rules for GURPS. Most of the material is for GURPS 3rd ed, but some titbits can be used for GURPS 4th ed.
Nolinquisitor has piled up dozens and dozens of videos on Youtube on many RPG topics. Reviews, Q&A, game sessions: the channels has everything and features quite a few videos on GURPS, ranging from reviews to practical advice on combat and including a 3-hour long session of GURPS Sharknado!).
Curated by Patrick L. H. Burroughs (Celti), this wiki can be helpful to GURPS GMs looking to play with D&D 3rd ed. material: it features system conversion guidelines and templates for a Dragon Lance campaign as well as more generic game aids like character sheets in a variety of formats, a combat flowchart or NPC forms. It is worth noting some templates are available to play in The Dark Eye / Das Schwarze Auge setting.
Warren Wilson (Mook)’s website is loaded with material for GURPS: from fillable character sheets to detailed Combat examples, it even offers a handy Excel version of the complete list of official GURPS 4th Ed. templates SJGames forumites have been putting together for the past few years. By the way, Mook is also the author of How to be a GURPS GM!
General RPG sites
A huge, huge resource and reference site for GM and players of any RPG. They also publish electronic books with ready-made material and advice for GMs.
This is a weekly podcast by the famous Ken Hite and Robin Law. It can be described as part Q&A, part open discussion on many topics around RPGs and other kinds of games.
Stack Exchange makes asking all kinds of questions and getting quality answers very easy and worth your time. It touches on too many subjects to list here; each has its own dedicated sub-site. RPGs have not been forgotten: thousands of questions have found their answers over there. You can play with the tags to focus on a specific game.
Plot lists and generators
From Carolyn Kaufman. Just refresh the page to get new, instant ideas. Her website on proper writing is also full of useful advice.
This website has several generators, from plots to characters and places.
Curated by S. John Ross. A large collection of plots, each one provided with enough details to get you started very quickly.
BoardGameGeek has put together a procedure to randomise the Big List of RPG Plots. Be sure to have a look, be it only for its reliance on rolling 1d34!
Forgotten Realms setting
A very large collection of articles on each and every aspect of the Forgotten Realms. The direct access per year (e.g. 1358 Dale Reckoning) proves also very useful if you happen to rely on an old campaign set.
A rather old website, where many wise sages dwell who can tell everything about the Realms and whose memories go deep in the history of Aber-Toril. Some are even close relation to Ed Greenwood and have played his campaign for years and years… You don’t want to miss the forum, which is the heart of the website. They also run Q&A sessions with Ed (through a friend of his and fellow forumite), which is quite unique! They used to gather Realmslore articles in PDFs as well, but they haven’t done so recently. There still is much great material in there.
Science Fiction and Fantasy
Have you ever wondered what happened to Saruman after he died? Or why phaser rifles aren’t used more often? Find the answers in the Sci-Fi and Fantasy sub-site at Stack Exchange. This website serves both as an excellent Q&A resource and a fantastic starting point for discovering interesting sites all over the web.