[Daniel Andrade] has built a pretty cool mood lamp circuit. He was initially inspired by [Toon Beerton's] Ikea lamp, but found he just didn’t have the knowledge to proceed with the PIC processor. He rushed out and bought an arduino to begin learning. Once he figured out how to properly make a mood lamp function, he created a custom circuit to utilize an ATmega chip instead of his whole arduino. He’s now on his second revision of the circuit and is sharing all the files with whoever would like to download them.
His circuit utilizes a 3wRGB LED and any ATmega 8/168/328. He has left some space for expansion on the board as well just in case you’d like to add sensors of some kind (he mentions a temp sensor).