For PenguFlip, I used a tool similar to zwoptex. It automatically arranges images in a big texture atlas and saves the coordinates in the format that you can see in the demo application.
Unfortunately, I wrote that tool in the company I work for (funworld), so I cannot make it publicly available. (Furthermore, it's written in .Net, not exactly a Mac-friendly platform 😉 ). But you can be sure that in the next version of Sparrow, we will either support zwoptex (I have to evaluate that a little more), or have recreated the funworld tool using Ruby, Java or another platform-independent language.