Message me through Discord if you need links to any of the Discord servers. You can find some of the servers on Disboard or with a search on Archive Of Our Own.
Note that the average fan uses Mando'a as a cipher for English. A few have found the original or fan grammar guides and write a little more "authentically."
For a video (from a different person) offering an overview of the official development of Mando'a: https://www.youtube.com/watch?v=MZTqCn0BZwM
October 2004 - Republic Commando: Hard Contact, written by Karen Traviss. Karen Traviss receives the lyrics that Jesse Harlin created for the Republic Commando video-game soundtrack and begins the expansion of Mando'a from the 60+ "words" that Harlin created for the various songs. The novel contains two words of Mando'a in it: vod (from the Republic Commando soundtrack) and di'kut, which the author made up.
2004-2009 - Karen Traviss expands Mando'a to just over 1100 words and phrases (there are actually more words and phrases in the novels than appear in the dictionary).
Early February 2005 - Some songs are released on the promotional website before the actual game is released, and fans begin to expand on the lyrics into a "usable" language. This happens before Karen Traviss has done much work at all on the language, let alone made a version publicly available. In my research, I've found the original word list repeated in a few places, but I have not found anyone who's further expanded on it. There is a strong possibility that words taken from this original fan creation are what we hear in "The Mandalore Plot" of The Clone Wars (season 2, episode 12); however, no one from Lucasfilm has confirmed this. Credible rumor has it that the language was used widely in gaming forums, but those places are now defunct, so I can't provide links beyond the original word list. Song-based expansion that does not use the efforts of Traviss: https://www.swgemu.com/archive/scrapbookv51/data/20070127004230/index.html
February 28, 2005 - The Republic Commando soundtrack, by Jesse Harlin, is released.
February 16, 2006 - The Star Wars Hyperspace online site makes available to members the first public version of the wordlist and the grammar guide that Karen Traviss created for her use.
2004-2009 - A page dedicated to Mando'a is created on Wookieepedia and periodically updated with words from the novels, from posts by Karen Traviss, and the dictionary that was made publicly available (first on the starwars.com site, and later on the author's personal website). People use some of the words in various online forums, including trying to form sentences. Apparently, there are some poems and very short stories out there, but the data is hidden or lost.
2008 (more or less) - Sola'lor creates the now-defunct mand-alor.com and, among other activities, creates a new alphabet for Mando'a and a new grammar guide, which includes several new words. Backup of most of the site: https://web.archive.org/web/20081121224810/http://www.mand-alore.com/language.html ; Archive.org doesn't have the PDF, so I uploaded it to my site: https://drive.google.com/file/d/1zNlVBo9peJEd7d2VXvyMAHJBR5KofXck/view
After 2009 - After Karen Traviss more or less amicably quits Star Wars over creative differences, the author offers the grammar guide and word list that she created on her website for a few years and encourages fans to run with it. And boy-howdy, do they! Among the popular offshoots that I don't have dates for:
Coruscant Translator (KT's word list expanded with a custom variant of Esperanto): https://starwars.myrpg.org/coruscant_translator.php
LingoJam (this one is a top hit; for words not in its database, it keeps the English; uses KT's word list expanded with custom words derived only from that list): https://lingojam.com/Mandoa-EnglishTranslator ; same person created this: https://mylittlewordland.com/course/313474/mandalorian-beginners
Aliit Groxus (custom version for an online roleplaying group; the person expanding this apparently has linguistic training; they have a Discord server you can track down, if you like, though they don't use much Mando'a in the public spaces of the server; for words not in its database, it keeps the English; uses KT's word list expanded with custom words derived only from that list): https://lingojam.com/GroxusMandoa
Fan-fiction writers create new words as needed, largely without consulting with each other or even knowing that other people are also making new Mando'a words — often without ever having seen forums.mandoa.org and instead finding the original wordlist through Tumblr posts, posts on roleplaying forums, Wookieepedia, and so on. The number of new words likely exploded after the release of The Mandalorian show in 2019, though that is only speculation on my part. A doc with 10 pages of random links to fan contributions over the years can be found here (and that's still only a sampling of places with more than a few words!); there are practically as many variants as there are users of the language. Some expand only from the word list; others expand from one of the spreadsheets left by Tal'jair on the mandoa.org forums:
https://docs.google.com/document/d/1-9R37Qi2PII1dIX15TLc4xAFLZ96ZijTn2qQn8cJPqc/
2011 - Mandoa.org is created. The original word list is displayed as the landing page, typos and all, never to be updated, as part of an agreement of some kind with Lucasfilm. There's a post somewhere about that on the forums, I think. There's relatively frequent activity on the site for a few years, as people offer their insights, discuss ideas, and try to translate various works. The discussions on this site show how the majority of fans of Mando'a expand the language; very few contributors have any patience for doing deep and holistic dives into roots and even fewer have any experience with either linguistics or language construction. People work together more by accident of being in the right place at the right time than deliberately.
2013 - TooShortToBeStarbuck posts a collection of resources for Mando'a in the r/Mandoa subreddit (which was created in 2013);
2014 - The r/Mandojoha subreddit was created.
2015 - Tal'jair (soon after joining, it looks like) begins a thread containing a massive number of words. Later that year, Tal'jair releases the first version of "Total Guide to Mandalorian Language." This uses the MLD document as its base and expands the grammar and includes an expanded wordlist. The last page of the document includes acknowledgements. These acknowledgements are dropped from future versions. This 2015 PDF and the spreadsheet versions revised and updated in 2016 and 2017 were found by fans and spread around the Internet. Many fans use one of these versions as the basis for their versions of Mando'a. The most recent version available on the forums is from 2021; I don't think that one is as widely dispersed as the earlier ones. Tal'jair largely left in 2017 (or thereabouts), developing the language first in the Aay'han Russian Mandalorian realism Discord server and then later moving to a private server to discuss and develop the language with the rest of the Rusk clan.
2016 - Two different collections of Mando'a learning aids are posted in the r/Mandojoha subreddit: https://www.reddit.com/r/mandojoha/comments/5wp00v/mandoa_lessons_by_lenzero_deviantart/ and https://www.reddit.com/r/mandojoha/comments/6ag5ia/here_are_all_the_learningteaching_resources_i/ (the latter was also cross-posted at about the same time in the r/Mandalorian subreddit).
2017 - Two different Discord servers were created by members of the Mandoa.org forums to discuss Mando'a and Mandalorians - Aliit Sharal and a server that would later be known as the Oyu'baat. Because of this, much of the activity that used to take place on the forums went elsewhere. Meanwhile, the Tumblr blogger Miit'alor creates a Discord server (Gayi'kaab) to support that blog.
2019 - The Mandalorian show debuts and brings in scores of new fans of Mandalorians who have no idea about the books by Karen Traviss, and no idea about the very different culture presented in those books.
2020 - The MandoCreator server is created for support of the MandoCreator website. It does not have the language or community aspects that it has now.
2021 - A slew of Discord servers for discussing Mando'a and Mandalorians are formed: Mando'a Nerds, SW Conlangs (one of many Star Wars conlangs discussed here), Din Djarin/Boba Fett fan-fiction/AO3 support, Raysh'la Nari (found by the person who made this version of Mando'a, which is popular on AO3: https://www.tumblr.com/syntymatitahna ), Oya Biatch! fan-fiction/AO3 support, Project Shereshoy, and many more that I don't know about. No clue what was so special about this year.
2022 - Cin Vhetin establishes the MandoCreator version of Mando'a by adding a dictionary to the MandoCreator web site and forming a team of people to help expand Mando'a in a direction unlike what any other group or individual has done. Team members have experience with at least two Earth languages, and some have taken courses in linguistics and in language construction. The core members were part of both the Oyu'baat and MandoCreator Discord servers and have all done more than surface-level dives into the original Mando'a word list left by Karen Traviss and into potential roots seen in various words. All have made significant and varied contributions to the understanding of the original version of Mando'a.
2023 - Tal'jair and company create a website at mandoa.ru to host their version of Mando'a. Archive of Our Own adds "Mando'a" as a language option.
No later than 2023 - Pel'tigaan creates a website that combines a few large fan dictionaries (including citations as to which sources different words are from); it also includes new words created for this version of Mando'a. This is one of the first publicly visible attempts at collecting and documenting fan words from around the Internet. https://peltigaan.neocities.org/
2024 - Ranahan starts documenting on Tumblr (https://www.tumblr.com/ranahan ) an attempt to make a version of Mando'a that both follows the traditional kludgy way of forming words and a way that follows how Earth languages evolve over the centuries. This person speaks multiple languages and is a self-taught linguist. The Tumblr account also has reblogs of posts about Mandalorians, Republic clones, Star Wars, Earth languages, and anything else that Ranahan finds interesting.