Fun with water, great recycled plastic bottle project. This could be pretty if you used wine bottles. It's just a matter of figuring out how to cut a hole in the side.
I like this because it's playhouse-style and has a kitchen sink. It would be fun to have water plumbed to the sink for mixing mud pies and cakes.
Some ideas reminiscent of Minnetrista's Backyard Garden that you can do at hoime.