http://www.japaneseclass.jp/

Seems ok. Looks like mainly a test of vocabulary and kanji. You take tests, as you get questions correct you get "experience" points that let you take higher level tests. Getting questions correct in a row (5 then 10 then 20 where it increases more) nets bonus points.

Doing the random question tests at the end of levels nets bigger experience, so do that for earlier levels.

For some reason, the grammar portion requires you to type in the answer, but it resets your bonus count.