Wow what a great thread! I got my Wii and Balance Board for my birthday in July as an attempt to lose weight... and I put on a stone as it gained dust. It's now moved to a different TV, where I can get peace to play! And I'm aiming for an hour a day, I've also just bought the Wii Fit Plus too! It such great motivation seeing the calories you are burning!
I hadn't heard of the Wii Active until I read this thread, and it's on my list for Santa - as well as the Dance Mat for the Wii!
These challenges sound amazing - no-one else at home uses my wii, so it makes it difficult for me to challenge myself against someone but this sounds fab! Will definitely be joining in!