News
https://www.startrek.com/ - The official website for Star Trek
https://trektoday.com/content/ - An archive of Star Trek news.
Reference
https://trekcore.com/ - Star trek images, audio, video and reviews. Huge number of screencaps of every Star Trek episode.
https://memory-alpha.fandom.com/wiki/Portal:Main - An extensive collaborative Star Trek wiki about 'canon' Star Trek (what is seen on-screen).
https://memory-beta.fandom.com/wiki/Main_Page - Another extensive collaborative wiki about 'non-canon' Star Trek (books, comics, games, etc.)
https://www.ex-astris-scientia.org/ - Huge compendium on scientific, technical, artistic, social and philosophical aspects of Star Trek.
https://tvtropes.org/pmwiki/pmwiki.php/Franchise/StarTrek - TV Tropes Star Trek page
http://www.phasers.net/ - Everything you ever wanted to know about hand phasers
https://explaining-errors-in-star-trek.fandom.com/wiki/Explaining_errors_in_Star_Trek_Wiki - Explaining errors in Star Trek wiki
https://www.st-minutiae.com/ - As the name suggests, all about the little details in Star Trek
http://www.startrekmap.com/ - Star Trek maps
http://www.shipschematics.net/ - Sci-Fi ship schematics including Star Trek ships
https://startreksetplans.tumblr.com/ - Blueprints from Star Trek sets (not ship schematics, the actual shooting set plans).
https://roddenberry.x.io - The official Roddenberry archives. 3D navigable ship interiors.
Organizations
https://www.kli.org/ - The Klingon Language Institute
https://sfi.org/ - Starfleet International, the international fan organization
https://www.starfleet.center/ - STARFLEET, the oldest continuously-operating fan organization in the world.
https://www.trekfederation.com/ - Charity organization for fans to help with real-world problems.
Please add links below and I will edit this post. I want to avoid things like personal Twitter or Instagram pages from specific actors or this list will get ridiculously long.