conversational (more practical, less academic)
Immersive Chinese incremental fundamentals trainer
Loecsen audio dialogues + listening quizzes
Speechling audio phrasebook
Melnyks audio lessons
fun games for beginners
matching games
"Concentration" game & quizzes
identify Chinese characters
Fluent Forever tones + pinyin
quirks (semi-vowels, etc.)
Mandarin Blueprint pronunciation workshop
how to say j, q, x
YoyoChinese tone pairs practice
topic-comment structure research
Chinese with Xiaolu more native-like pronunciation
Rita Mandarin Chinese Northern accent: dropped sounds, érhuà, and more

ShuoShuo Chinese grammar points, incl 了
ChinesePod completed-action 了
change-of-state 了
emphasis 了
Chinese Zero to Hero grammar points
grammar wiki by level
word/character tools
flashcards Quizlet decks
dictionary/flashcard mobile app Pleco
Chinese-English dictionary; related words/compounds YellowBridge
dictionary w/regional usage notes Wiktionary
character/component ref tool HSK word lists
dictionary; detailed definitions & examples; in Chinese Taiwan Ministry of Education
Day Day Up
FSI (Foreign Service Institute) textbooks & materials best explanations of Mandarin tones
HSK standard textbooks & materials lessons