Sound Junction
Is It Any Good?
The neat thing is that anyone can build a personal trail and save it for future use. Education professionals can make accounts as advanced users and create trails for others to follow.
The site takes some time to learn to use, so don't visit thinking you're going to have a quick look and listen. The site is aimed at high school-aged kids, although parents of younger children could preview the site to find sections that might be fun for younger kids to manipulate.

Become a member and get recommendations from other parents based on your child's age.