"This site explains Japanese grammar in a systematic step-by-step process and is released under the Creative Commons License. It was created as a resource for those who want to learn Japanese grammar in a rational, intuitive way that makes sense in Japanese. The explanations are focused on how to make sense of the grammar not from English but from a Japanese point of view. To learn more about this guide, go to the introduction page and start learning this intriguing and unique language!".
There is a web page version, although, there is a version available to download (sip file or pdf). Also, the page is translated into different languages: German, English, Spanish, French, Bahasa, Italian, Polish, Portuguese, Russian, Finish, Turkish and Korean.
- A Japanese guide to Japanese grammar: http://www.guidetojapanese.org
The second one is Charles Kelly's Online Japanese Language Study Materials. As Charles Kelly states "these are free-to-use online materials that I have developed to help people learn Japanese."
This site is an interesting tool to practice the use of the language with quizzes, vocabulary exercices, flashcards, crossword puzzles, videos and so on. It's got a selection of Japanese language study sites to find more resources to learn this language.
- Charles Kelly's Online Japanese Language Study Materials: http://www.manythings.org/japanese/