I haven't seen any in our neck of the woods yet, but in many parts of the world cargo bikes, which come in all shapes and sizes, are becoming more popular. Just like regular bikes, they're a great way to save money on transportation and enable you to carry more groceries, people, or whatever else you need to transport, and get your exercise at the same time. And it's fun! I tried a Bullitt cargo bike last year. It has a bucket in the front, and it has two wheels. It took a bit of getting used to, but you get the hang of it pretty quick. Not sure how wobbly it might be when it's got a full load though. Anyway, here's a good article from Next American City about cargo bikes and their rising popularity.