A good place to start is Tae Kim's website here:
Tae Kim's Japanese guide to Japanese grammar
He explains Japanese language from the writing systems and basics of grammar, all the way to some more "advanced" grammar structures.
Make sure you read through the Introduction page to find out exactly what his guide covers and what it does not cover.
You will need to learn how to read Hiragana and Katakana before you can really progress through his website, but they don't take very long to learn and he has a section covering the writing systems anyway.
Luckily once you get past the writing systems and the different way of thinking, Japanese (In my opinion) turns out to be quite an easy language to learn.
Good Luck
