tools

Logging, Journaling, and Communication
tools and apps for logging information about your system, sending messages to each other

Simply Plural - by Apparyllis - an app designed specifically for systems for documenting, switch logging, and more! (Google Play/Apple Store)

Notion - by Notion Labs, Inc. - frequently used by systems to document information, this app allows you to create and use templates for databases, calendars, galleries, and more! There are plenty of system-related templates already on there. https://www.notion.so/product 

Daylio - by Habitics - also frequently used by systems, this is a basic mood tracker and journaling app with a lot of functionality. (Website/Google Play/Apple Store)

Chat Journal - by Agiletelescope - a chat-style journaling app with a tagging system and the ability to create multiple pages. (Google Play)

TwiNote - by Chartreux - a Twitter-style notes app. You can make an unlimited number of "accounts" and make "tweets" from those accounts (none of which are actually public). (Google Play/Apple Store) 

Antar - by Antar - a chatting app that lets you create, switch, and text with different "personas" and "emotions".  (Google Play/Apple Store)

Mapping/Worldbuilding
tools for making maps of headspace and logging inner world information

Inkarnate - by Inkarnate Entertainment LLC - geared towards writers and roleplayers, this site lets you create flat maps, from anything as small as a tavern to as big as a planet. You can color terrains, use stamps to add plants and rocks, and more. There is a free trial, and lots more features for a decently-priced subscription. https://inkarnate.com/ 

World Anvil - by Chronos - a set of writing and worldbuilding tools; you can make character profiles, wiki-like articles, interactive maps, historical timelines, and even full novels! Most of this is available with the free trial, however, privating your work requires a paid subscription. https://www.worldanvil.com/ 

Campfire - by Campfire Technology LLC - another set of writing/worldbuilding tools similar to World Anvil with much of the same features. Also has a free trial and an optional subscription to access more features. https://www.campfirewriting.com/

Discord Bots
bots for Discord specifically 

PluralKit - by Astrid - the most popular bot for systems. It allows you to make profiles with information about various headmates, add them to groups, and most importantly send messages with webhooks as a given headmate. The bot will delete your message when prompted by a tag (such as an emoji or letter/name) or the autoproxy feature, then re-send that message using a webhook with the given member's name and icon. The bot is open source, so you can make a fork of it for your own personal usage. Join the support server listed on the website for assistance with PluralKit, and for external tools/sites that work with it. https://pluralkit.me/

Tupperbox - by Roryl - another popular proxy bot with many of the same features as PluralKit. This one is used more frequently in roleplaying and tulpa communities, but is still popular with other general plural spaces. https://tupperbox.app/

Names
resources for figuring out or choosing a name

Behind the Name - by Mike Campbell - gives names and their meanings/origins; has many search parameters; best for this-world names. (Given Names/Surnames)

Fantasy Name Generators - by Emily - has loads of generators for names of people, places, groups, and more! It mostly features fantasy-esque names, but also has supernatural and real-world names. Also explains the patterns and structures of the names offered by a given generator. https://www.fantasynamegenerators.com/ 

Nameberry - by Pamela Redmond and Linda Rosenkrantz - a decently popular baby name website that lists, categorizes, and defines names. https://nameberry.com/

Pronouns
lists of pronouns and tools for testing out pronouns

Pronouny - by noa - has a massive collection of pronouns, neopronouns, nounpronouns, emoji pronouns, etc; also allows you to list and share your preferred names/pronouns with others. https://pronouny.xyz/ 

Pronouns.page - by Rada Języka Neutralnego - lists and explains various pronoun sets; also allows you to list pronouns, names, and LGBTQ+ identities in cards to share with others. https://en.pronouns.page/pronouns

Pronoun Dressing Room - by Sal the Human - lets you input a name and pronouns and will give you some sentences using those names and pronouns, including some passages from a few novels. Also has a small selection of pronouns with different categorizations and themes. http://www.pronouns.failedslacker.com/ 

English Neutral Pronouns - by various - a wiki page listing various traditional and neopronouns used in English. https://nonbinary.miraheze.org/wiki/English_neutral_pronouns 

Gender/Orientation
for figuring out things about your gender(s) or orientation(s)

Wikis - by various - There are countless resources out there for LGBTQ+ folks to peruse. These are just starting points and are not by any means exhaustive; many other identities are coined and/or exclusively found on Tumblr and sometimes Twitter.

https://lgbta.miraheze.org/wiki/LGBTA_Wiki 

https://nonbinary.wiki/wiki/Main_Page 

https://nonbinary.miraheze.org/wiki/Main_Page 

https://mogaiwiki.miraheze.org/wiki/Main_Page

Avatars/Icons
sites and apps where you can make images or models of yourself

Picrew - by TetraChroma Inc. - a huge website of diverse avatar creators made by different artists. Anyone can make their own and submit it to the website. It's rather difficult to navigate but there's definitely something for everyone! There are even some makers for non-humans, furries, animals, objects, scenes, and even some pride flags and pronouns buttons. The site is primarily in Japanese but is relatively intuitive for speakers of any language, and there are plenty of non-JP speakers that make content for it. MOBILE-FRIENDLY https://picrew.me/ 

Charat - by LIBRE Inc. - a collection of avatar makers in a similar style, with a diverse selection of items and an RGB color picker (in addition to pre-set colors); you can also add patterns to some items. Most avatar makers are human, but there are a few cat makers. MOBILE-FRIENDLY https://charat.me/ 

My Webtoon Character - by Hellotoon Inc. - a personal favorite of our system. Has a diverse selection of parts, items, and colors. You can even make group pictures and fit potentially infinite characters/items/stickers on the scenes. From what we know there are infinite character slots. MOBILE ONLY (Google Play/Apple Store)

"Gacha" series - by Lunime Inc. - there are several games in this series, most notably Gacha Life, Gacha Studio, and Gacha Club. They're all in a chibi anime style, and you can save multiple characters. There's a lot of customization to be had with these apps, and you can even make scenes with multiple avatars. Options vary slightly between games, but for the most part they're the same. MOBILE-FRIENDLY (Dev's Google Play profile/Dev's Apple Store profile/Dev's Itch.io profile)

Various - Though most of the sites listed below have become obsolete due to Adobe Flash no longer being supported by browsers, the sites still do have some useful and diverse dress-up games. Many have a childish, cartoonish, or storybook-esque style. Most are feminine and human, but there are some masc/neutral and non-human options. A lot of them have overlaps in content and host/integrate avatar makers from other sites. NOT MOBILE-FRIENDLY
Azalea's Dress up Dolls - https://www.azaleasdolls.com/index.php
Dress Up Games - https://www.dressupgames.com/
Doll Divine - by Ola - https://www.dolldivine.com/
Pastelkatto Games - by Billie/Pastelkatto - https://pastelkattogames.com/
Kawaii Games - by Heglaé Maia - https://www.kawaiigames.net/ 

Miscellaneous
other useful things

Flowcharty - by The Collective - a simple but useful tool to help blurry/blendy/unknown members figure out who they are. Insert traits associated with various headmates, and the site will ask yes/no questions to help you figure out who you are or aren't via process of elimination. https://flowcharty.altervista.org/ 

Akinator - by Elokence - mostly useful for fictives and factives, this app asks you questions about a character and tries to guess the character you're thinking of, so it can be useful for someone who knows that they're a fictive or factive but isn't sure who they are. (Website/Google Play/Apple Store)

Artbreeder - by Joel and others - an AI-powered art tool that can be used to generate and alter images of people, places, objects, and more! Can be useful for making images of headmates and headspace. https://www.artbreeder.com/