List of languages

Deutsch ~ German

Deutsch Plus
Video series in easy German. Unfortunately, some videos are blocked in some/all countries.

Deutsch Direkt
An old video series to learn German.

Goethe-Institut videos
Including Mein Weg nach Deutschland, etc.

Français ~ French

Coming soon...

Italiano ~ Italian

Coming soon...

日本語 ~ Japanese

Itazuraneko

/jp/ DJT website. Many, many resources, and useful guides.

How to learn hiragana and katakana

Hiragana and katakana, collectively referred to as kana, are two of the most important writing systems used in the Japanese language.
You should learn these at the start of your Japanese learning journey. The sooner, the better.
Unfortunately, a lot of textbooks give a brief explanation about hiragana and katakana
and a table of the characters, and expect you to have them magically memorised by the next chapter.
Here I give you a practical guide on how to actually learn and memorise kana.

Definitely read The Writing System chapter by Tae Kim.
Optionally, you can read Tofugu's hiragana and katakana learning guides with mnemonics.
Alternatively, you could optionally read Heisig's Remembering the Kana (not to be confused with Remembering the Kanji). This also has mnemonics.
Definitely check out this mnemonic to remember the katakana shi and tsu.

It's highly recommended to learn how to write hiragana and katakana, even if you think you won't need that skill.
Print these hiragana and katakana writing sheets.
Use these online, free kana flashcards from Itazuraneko.
Learn install a Japanese keyboard here. This guide doesn't cover Linux unfortunately.
Maybe this guide on typing in Japanese might come in handy, too?

A Guide to Japanese Grammar: A Japanese approach to learning Japanese grammar

A free, online grammar guide.
Commonly referred to as Tae Kim, the author's name.
Don't skip The Writing System chapter if you can, even if you already learnt kana.
Also available as a paperback, PDF, and mobile apps (iOS/Android).
Ignore Tae Kim's Complete Guide, which is incomplete.

WaniKani

Online website. SRS for kanji with mnemonics. Requires registration. Paid. There's a sale every Christmas/New Years period.
The 3 first levels (out of 60) are free, so try those out to see if it's for you or not.
If you find it too slow, it will get faster very quickly.
They also have an online community (forums).

Erin's Challenge! I can speak Japanese.

Website with videos. Made by the Japan Foundation. Requires Flash Player.

Let's Learn Japanese Basic I

Old video series by the Japan Foundation.
Features skits with Yan-san, Mine-san, Sugihara-san, and Kaihō-san with explanations by Althaus-sensei.
Wikipedia article

Let's Learn Japanese Basic II

Nihongo con Teppei for Beginners

Podcast spoken in easy-to-understand Japanese.
Episodes are about five minutes long. The early episodes are very easy, but it gets more interesting quickly enough.
This is a spin-off of Nihongo con Teppei (see below).
Apple Podcasts (US)
Castbox

Nihongo con Teppei

Podcast for intermediate speakers.
Episodes are about 20~30 minutes long?
iTunes (US)
Apple Podcasts (US)
Castbox

JF Japanese e-Learning Minato

An online course by the Japan Foundation.

Pусский ~ Russian

Russisch bitte!
A German video series.

Russian World with Vera Polyakova-Norwood
A video series.

Pushkin Institute
An online course by the Pushkin Institute.

Svenska ~ Swedish

Learning Swedish
An online course.

Pimsleur
Audio lessons where you learn to speak by repeating. It's a bit America-centric. Paid, but there are alternative ways to get it.

Colloquial Swedish (2nd edition, 1996)
A book with audio cassette. MP3s of the audio exist if you know where to look.