Go here for a great explination of Charliplexing.
I've actually made a kit for this, and I'm now taking pre-orders on my website. I also created a flash-based animation programmer. Check them out and let me know what you think. The programmer generates the newest version of the code, so it will still be a useful tool if you make your own heart. You will just need to change out the LED array with one that maps to your own.
I've updated the software to v 1.3. I found a function called PROGMEM in the avr/pgmspace.h library (included with Arduino software) that allows you to write directly to the Flash ROM. That now gives about 500+ frames of animation, and is an extremely easy thing to implement. You can check out the new software here.
Two of my friends are currently working on getting a bitmath version that should increase this even further (to around 4,500 frames), but while working, it is not very easy to work with in creating animations. I'll release that once I have my Processing program up and generating the animation codes.
I've put the schematic on step 1. There is a direct link to it on my flickr as well.