If you are a fan of Krashen’s research then you will love Rosetta Stone. I agree with a lot of what Krashen says, but think that most people take it too far.
I love Rosetta Stone. Right now I am learning Polish Level 3 and am able to use it extensively while traveling to Poland. I highly and enthusiastically recommend this product to anyone.
Their approach is definitely not for every one - it's very experiential, supposedly mimicking the way a child learns, and if you need to have grammar structure and rules laid out for you to understand it better, it may drive you crazy. And if you decide you like it, you may be able to get a better deal on eBay or Craigslist. I LOVE Rosetta Stone, and feel it's a wonderful way to learn a language. Kids especially should enjoy it, because it turns learning into a game. The downside is the expense - I bought an Italian level for a friend as a gift for hosting us for a week in Boston; it was a huge chunk of change, but a terrific gift for an opera buff.
Here's why your child will love Rosetta Stone® Kids Lingo Language Games: Simply put, they're fun. Easy to use. And kid-tested.