These will more likely be listed in the order that I think of them rather than by value, but every resource I list here should be valuable and most of them will be free to use.
Learn Hiragana: The Ultimate Guide by Koichi
This is on the homepage too, but it's very fundamental so this list would not be complete without it.
The Difference Between 「に」 vs「へ by JPLT Dialog+
I had this article open to review a nuanced grammar point, it's useful but may be more of a later-beginner level article.
This is an online guide which is also available as a PDF, it contains many grammar points and has been useful to me in the past. It's always recommended in threads about learning grammar.
This channel has good playlists for beginner grammar. N5 is first, then N4. The main channel had more, but I am hoping the new lists are as good as the ones I watched years ago.
This is a good website which is free with a library card in *most* US library systems. I do not use it much anymore because it has some weird translations that are... too stringent when testing comprehension. It's more useful at the beginning level.
This would be my #1 recommendation for a single website/app to learn basics with. At the early levels it teaches Hiragana and eventually even basic Kanji. It does this very slowly so it's better for complete beginners than someone like me, who already knew how to read the kana.
How to Learn Japanese Vocabulary by Hey Learning
I personally made use of memrise and anki more than anything else. I have some good anki decks that I could share, but they require hiragana reading.