Imabi is a thorough website that teaches Japanese vocabulary and grammar through text-based lessons. There are over 400 lessons that cover beginner to advanced topics, including over 30 lessons that teach classical Japanese.
The website is entirely text-based and should probably not be used as a standalone resource, as there are no audio files and only occasional exercises. However, there are lots of thorough explanations and extensive examples of how to use new concepts in various contexts.
Becoming a member gives you access to four kanji lessons that cover 60 characters. In these lessons, you will receive a basic explanation of the kanji, learn how it is used in a list of words, and differentiate between different readings. It is important to already have a strong grasp of hiragana and katakana before taking on these lessons.
Overall, it is a comprehensive and well-organized reference guide to support your Japanese studies. You can also check out Tae Kim’s Guide to Learning Japanese, another free resource for learning Japanese. It has similar text-based explanations, but also some accompanying videos and comics.