A list of resources for learning Chinese with updates based on previous comments. Open source software is listed in bold

--- Learning Apps ---

HelloChinese - similar to Duolingo, has adapted reading and flashcards, only HSK 1 level content is free

Duolingo - does not need introduction

Du Chinese - adapted reading, few lessons are free

--- Flashcard Apps ---

Anki has mobile, desktop and web versions

TOFU Learn - mobile app that supports writing Chinese with touchscreen

Wuxia Learn is WIP, some people may find it useful

--- Dictionaries ---

Pleco has a great mobile version

MDBG has a decent web version

Dong Chinese Wiki has character etymologies making learning characters easier

Yabla

Hanbook calls itself a dictionary with smart learning

--- Language Exchange ---

HelloTalk

--- Youtube ---

ShuoShuoChinese兑兑中文 has lessons for levels up to HSK4, interviews in Chinese, entertaining content

Grace Mandarin Chinese has amazing unstructured lessons with both traditional and simplified characters, slightly focused on Taiwan, China

Everyday Chinese has a lot of "Real Chinese Conversations" for beginner language immersion

Mandarin Corner has street interviews with subtitles (pinyin & translation included), perfect for HSK 3 immersion, speakers can have provincial accents

Chinese Zero-to-Hero has high quality Chinese grammar lessons for all levels HSK 1-9

--- Movies, series & cartoons ---

领风者 / The Leader on Youtube is an anime series about Karl Marx, requires good Chinese

Born To Love You (2013) on YT is a romantic movie

Peppa Pig available on Youtube but no subtitles, all inclusive for family, HSK 2-3 language

iPartment available on Youtube. Review from another Lemmygradian: "It's a sitcom based in Shanghai and is pretty Western, so you can understand what's going on even if you don't speak any Chinese. Read the synopsis on Wikipedia if you're in this boat. I watched it before I passed HSK 1 and picked up a few things, but there's certainly value to just listening and getting used to how spoken Mandarin sounds. I went back once I passed HSK 4 and started watching it again and was able to understand a lot more of the "Why" things were happening"