Look into WS2803. Only appears to be purchasable from a place in Niagara Falls, NY on e-bay.
I bought a tube of 25, haven't tried them out yet. Too many other projects going on.
Each WS2803 has 18 IO pins to drive 6 RGB LEDs with full PWM control.
TLC5940 is another option, wiht 16 PWM'able IO.
WS2801, does 1 RGB LED. Designed for daisy chaining.
WS2803-preliminary-En.pdf (437 KB)
WS2801.pdf (423 KB)
TLC5940 PWM driver.pdf (1.06 MB)