Here is my entry. It basically allows you to embed the open-source ads from Meta in your blog, etc.
It is simply a .js file you can include on the page.
My evaluation: Soapi.js is a very intuitive library for JavaScript. And by that, I mean the methods are laid out in a way that you would expect them to be. The whole thing is relatively self-documenting and integrates well with my above-mentioned application. I especially like the fact that API changes don't require a huge code rewrite - only a quick download!