You'll never guess what I'm researching at the moment!!!
In my (rather fruitless) search for Japanese language materials to use with my son, I've come across a couple of sites with songs for kids.
http://www3.u-toyama.ac.jp/niho/song/song_jplevel.html - these are actually graded by language level
http://hukumusume.com/douwa/index.html I'm still hoping for some kind of course materials that can be used by a non-Japanese speaker to learn together with my son. So far no luck