Feel free to contact me on twitter @jbtenmatay if you want to include a tool or resource.
Weblio Japanese to Japanese Dictionary
Weblio Japanese to English Dictionary
Weblio Japanese to Japanese Thesaurus
https://gogen-yurai.jp/ - Etymological J-J dictionary. Detailed explanations and synonyms for words and slang.
https://meaning.jp/ - Etymological J-J resource. Helpful for [word]とは searches.
goo.ne.jp Japanese to Japanese Dictionary
goo.ne.jp English to Japanese Dictionary
ichi.moe - Breaks down sentences into their constituent words, which are provided definitions courtesy of JMDict.
Immersion Kit - Easily search Japanese vocab and grammar across anime, drama, games, news, and literature.
Tools and offline dictionaries
http://qolibri.osdn.jp/ - browse and search EPWING format dictionaries (can be found online)
http://jedict.com/ - iOS app
https://www.tagaini.net/ - Offline J-E dictionary with other features that don't usually come with such programs
https://takoboto.jp/ - Available both online and offline
https://kanji.sljfaq.org/ - Supports a variety of ways to lookup kanji—handwritten, radical, SKIP, etc.
https://kanjitomo.net/ - Kanji OCR Tool
fugashi - Japanese tokenizer and morphological analysis tool
Japanese Sound Effects (SFX)
Japanese SFX Google sheet
Hentai and Non-Hentai Sound Effects and What They Mean (PDF)
Name kanji reading and katakana names
https://www.kanshudo.com/searchn - E-J name kanji lookup
https://www.weblio.jp/cat/dictionary/gkjyj - looks up possible spellings for katakana names (J-E and E-J)
English writing tools
WordWeb - Offline dictionary and thesaurus
E-J Fighting Game Glossary
The Chicago Manual of Style Online: Hyphenation Table
The Art of Writing Effective Queries
Green’s Dictionary of Slang - Comprehensive dictionary of English slang that includes sources and quotes, with tons of search options. A good way to check how if such-and-such slang is still being used and how.
https://www.rhymezone.com/ - Not just a zone for rhymes.
https://www.english-corpora.org/coca/ - Corpus of American English that searches through all sorts of text. Constantly updated but requires a free (but limited) account to use.
Merriam-Webster Dictionary and Thesaurus
Netflix English Timed Text Style Guide
Regular Expressions (Regex)
Regular Expressions: an Introduction for Translators
English resources for reading
List of Generic and Genericized Trademarks
Appropriate Terms to Use About Disability
A Fair Point Ensuring Gender Neutrality in Translation
Edging Toward Japan: Just how gender neutral is Japanese?
Queering Translation, Translating the Queer: Theory, Practice, Activism
Translation by Example: Principles for Minimizing Errors
J-En Translations - Interviews, podcasts, info about translation competitions, and other informative posts
Are your Japanese translations sounding robotic? Opt for the human touch.
Takashi's Japanese Dictionary - Good source to learn about the quirkier aspects of JP, complete with sentences. Also features some nifty tools.
Literary Translators Comment on Localization & Re-Translation
Monthly Slang Reviews
Can a Translation Be Better Than the Original Book
Capcom’s quest to translate The Great Ace Attorney for Western audiences
What the different カッコ (quotation marks) in Japanese are and how they're used
(Quora) How do you spell out sexual moans
List of Japanese Abbreviated Words and Phrases
The possibilities of research on fujoshi in Japan
Project Management in Game Development
Best Practices for Game Localization
Game localisation: unleashing imagination with 'restricted' translation
Redundant Translations in Games & Anime
XSEED Games blog
Videos talking about Translation
Tackling Translation: Media Localization Across Mediums (EN/日本語)
Thinking Outside the Panel: Critical Thinking for Simulpub Manga Translation
Other resource lists
J-E Resource Sheet by @usagiko
Living Japanese Slang Dictionary by Wes Robertson
Japanese Online FPS Game Terms Flashcard Set (Starter Pack) by Tomoyo
(JP-JP) List of gamedev-specific terms