Yes, you can use this site. I believe it contains about all Grammar of the Genki 1 and the Genki 2 textbooks. In the grammar explainations the site also uses example sentences which I really like.
There's also Tae Kim's Guide to Learning Japanese: www.guidetojapanese.org/learn/
It has a lot of stuff, i believe there's also an android app you can use to access most or all of the content in the website