You could also look at WS2803, can drive 18 LEDs (or 6 RGB LEDs) each.
These guys are the only ones carrying them that I've seen.
I bought 25 (DIP) recently but haven't done anything with them yet.
http://stores.ebay.com/NooElec/_i.html?_nkw=ws2803&submit=Search&_sid=32165772
WS2803-preliminary-En.pdf (437 KB)