Here's the screensaver version of one of the installations I did at the Glenfiddich One Day You Will Summit. It's a camera toy that has different types of fish swimming around, which you can interact with through your webcam.
To install, unzip it, and double click the resulting file. It should work for most modern mac laptops and iMacs with Mac OS 10.6 or higher installed. Please let me know if it doesn't work!
To get it to work as a screensaver, I had to compile openframeworks in 64bit, which you can find here.