A list of 100 things you want to do before you die. By itself this is not a very creative idea but, how about doing that social? You can create a page that you can customize, get friends connected to share your page, copy your items, help you to mark done items and get suggestions. Also a marketplace would help you realize the goal by matching local business that offer services to help you get things done.
100 Might be too high of a number, needs to be an odd number, 97, 65 – something like that, it is jsut more pleasing.