Anki
"Anki is a free and open-source flashcard program using spaced repetition, a technique from cognitive science for fast and long-lasting memorization." -Wikipedia
Language Reactor
"Language Reactor is a powerful toolbox for learning languages. It helps you to discover, understand, and learn from native materials. Studying will become more effective, interesting, and enjoyable!"
Language Learning with YouTube and
Language Learning with Netflix
These are extensions that allow you to have dual subtitles on YouTube and Netflix videos, look up the meaning of a word, and so on. I've only used the YouTube one so far, but I like it a lot. Personally, I have it set so that the English subtitles are hidden unless I choose to reveal them.
CaptionPop
This is the same general idea as Language Learning with YouTube, but it's a website instead of an extension. I prefer LLWY because the subtitles are on the video while with CaptionPop they're below the video. I use this one on my iPad sometimes though.
Drops
Drops is an app for learning vocabulary and phrases. You can see the available languages
here.
Forvo
Forvo is a pronunciation dictionary. You can search words, phrases, and sentences to see if anyone has uploaded themselves saying the given word, phrase, or sentence. Users can request pronunciations of words, phrases, and sentences, and other users can upload their pronunciations. I use this site to get audio for some of my Anki cards.
LangCorrect
"Master grammar, spelling, and syntax in the language(s) you’re learning through direct feedback on your writing from fluent, native speakers."
Polylogger
This is a site for logging your language learning.
InterPolly
"Watch YouTube videos and develop your vocabulary quickly."
Available languages: English, French, German, Italian, and Spanish
Refold
"The Refold roadmap is a step-by-step guide for learning any language from scratch. We explain exactly how to combine media, strategic study, and educational technologies to achieve high-level language fluency faster than any other method in the world."
If you're new to language learning, then I think there are a lot of helpful tips here as to how to go about learning a language. Of course, everyone has their own methods, and I only recently learned about this site myself, so use the info on this site it if you'd like, and don't use it if you don't want to.
Voracious
"A video player for learning languages (esp. Japanese)"
Migaku
"If you want to learn to speak, and more importantly, understand a language the way a native speaker does, then immersion is the only path. Migaku is here to help you on that journey, from your first steps, until you reach fluency and beyond!"
Learning With Texts
"The goal of Learning with Texts is to learn a foreign language while you read books, articles, or any text you want. When you find a word you don’t know, click on the word to bring up an online dictionary. Enter the definition you want and choose a status between 1-5 how well you know the word. Unfamiliar words will have a red background and familiar words will appear green. The goal is to move words from red (1) to green (5) by seeing the words used in context many times. Definitions are saved across texts and can be displayed above the word. LWT also has a built in audio player for text with an accompanying audio."
Tatoeba
"Tatoeba is a collection of sentences and translations. It's collaborative, open, free and even addictive."
Readlang
"Learn a language by reading whatever you like. Translate words & phrases live on any web page. Use these words to practice flashcards."
Filmot
Search YouTube for videos with subtitles in specific languages or videos with a specific word/phrase.
Zero To Hero
"This is a platform that provides tens of thousands of videos with subtitles and dictionary tools across hundreds of languages!"