A random assortment of interesting sailing sites, in no particular order.

Minimus II
A junk rigged 24 foot instant build (MCO fiberglassed plywood) catamaran for trade wind crossings. Hull influenced by Wharrams.

Junk Rig Association
"The JRA (Junk Rig Association), formed in 1980, aims to further the development of the junk rig and to create an international community of people interested in such rigs to share experience and ideas." JRA has good reference materials for junk rigs. Practical Junk Rig - by H.G. Hasler seems the authoritative reference book on the subject. Junk rigs are stable, easily controlled and reefed, if perhaps less efficient in some ways.

De Villiers Design
Boat designs by David de Villiers, particularly the recent (as of 2023) DS 525 Cruising Catamaran - Design #237 a 15-ton, 16-meter, quasi-performance 5083 Aluminum cruising catamaran. His earlier forward cockpit designs remind of Chris White cats, but done in Aluminum.
Here's a YouTube interview with David de Villiers.

Balance Catamarans
Phil Berman's South African plastic composite catamarans with a good balance of performance and comfort with clean and modern styling. As founder of The Multihull Company, Phil brokered hundreds of multihulls, and he synthesized tons of experience and design thoughts learned from those into Balance yachts. Phil was also a world champion Hobiecat racer, and he has a racer's clean and mimimalist aesthetic. Phil's book on catamaran sailing is available as: Catamaran Sailing: From Start to Finish

Mumby 48
An aluminum performance catamaran built on Cebu Island in the Philippines by Australian Tim Mumby. The link above is to the site of Jupiter 2. Designed cruising displacement is a very light 7.4 tons. Fully equipped price was $300k USD, now about $400k, still about 1/3 as much as a first or second world cat of similar size. A Facebook page about Mumbys doesn't have nearly as much information about the boats as Jupiter's.
Jupiter 2 owner Jamie has great Mumby 48 overviews on his YouTube channel including: hull build, fit out, design features, questions and answers, and an interview with Tim Mumby.

Odisea Yachts
Performance Aluminum catamarans built at a professional yard in Viet Nam. Peter from the Sailing Into Freedom Youtube channel mentioned that the Odisea 48 is based on the Mumby 48, and is being advised by Tim Mumby in addition to having a professional naval architect and structural engineer on staff at Odisea.

James Wharram Designs
James Wharram is one of the pioneers of making Polynesian influenced multihulls popular in the West, along with Chris White, Jim Brown, etc., later. His Tiki 38 is a classic self-build in fiberglassed plywood. Sail handling is particularly pragmatic and simple, especially on the smaller Wharrams.

HH Catamarans
High performance plastic composite catamarans built in China by the Hakes of Australia. Designs are by top American naval architects Morrelli & Melvin. Morrelli & Melvin designed many America's Cup boats, for example. HH is reportedly setting up a factory in The Philippines.

Seawind Catamarans
Plastic composite catamarans originally from Australia, now built in Vietnam. Parent company Corsair Marine also builds multihulls (trimarans) and owns Rapido trimarans. All under the same roof in Vietnam now.

KatieKat
A site about the Siudzinski's Australian-built 2000 Seawind 1000.

Corsair Marine
Corsair builds plastic composite trimarans in Vietnam. The designs probably descend from Ian Farrier, particularly his F-27.

Rapido Trimarans
Performance plastic composite trimarans built in Vietnam. Designed by Morrelli & Melvin.

Chris White Designs
Performance plastic composite catamaran designs by American Chris White are highly admired for performance, ergonomics, comfort. Chris is one of the second generation of pioneers of Western multihulls. His book The Cruising Multihull is a top reference for multihull concepts, along with Jim Brown's The Case for the Cruising Trimaran. Here's an interview with Chris White by the O'Kelleys.

Outremer
Performance plastic composite catamarans built in France. VPLP naval architecture. The O'Kelleys have a great Outremer factory tour on their tech YouTube channel.

Windelo Catamaran
Performance plastic composite catamarans built in France. Innovative features such as a nearly monolithic salon/afterdeck, lighter/simpler design, semi-enclosed front helm, and somewhat environmentally friendlier composites, for example using basalt fibers. Here's a video tour of their Windelo 50 Adventure. He's an interview about a 11,000 mile Windelo 54 Adventure shakedown cruise that was made very easy by a very well designed boat.

American Sailing Association
"ASA is an association of sailing schools, charter companies, professional sailing instructors, and sailors."

NauticEd
Online sailing classes, logbook.

North Sails Blog
North Sails Blog has lots of good information, but doesn't seem usefully indexed. I found it by searching for sail twist and found this nice article by champion racer and sailing instructor Bill Gladstone. It seems related to his article on upwind sail power, and "Full Power & Mix Of Power".

OpenCPN
Open source chart plotter and navigation software with tons of sailing plugins.

OpenPlotter
Open source chart plotter with Raspberry OS disk images available. Includes OpenCPN and more.

Yachting World test of Beneteau's soft wingsail
In 2014, Beneteau experimented with a soft wingsail that could be reefed like a conventional sail. It has symmetrical airfoil shaped battens on the front half (luff) of the sail with conventional sail aft of that. The airfoil section streamlines the mast and halyard for reduced drag and cleaner airflow.
The soft wingsail sail reefs and stows to the boom like a typical mainsail, addressing the concern that rigid wingsails can't be reefed in high winds. At least in part because of that, this seems like one of the more potentially practical implementations of a wingsail for recreational boats. Unfortunately it has not gone into production.

Bellmarine Electric Propulsion Systems
One of many electric drive makers for boats. Used by Windelo, for example.

MG Energy Systems
Makers of batteries and battery management system used by Windelo.