I have built the online room colour painter for Crown Paints through the lovely company Code Computerlove. Through this feature a user can go and paint five different rooms in real time and see the results in either day or night, using AS3 and Papervision to navigate around the 3D environment.
A nice feature is that what ever the main colour the user has selected the site will bring back related approved Crown Paints colour schemes. Some nice UI touches with drag and drop when re-arranging the colours in the scheme.
This site has recently just been voted the best of its of kind for best brand development at this years Big Chip awards, see more here.