The NASA Astronomy Picture of the Day always has something spectacular. The picture above, from 21 December last year, shows a montage of images taken at different wavelengths by NASA’s Solar Dynamics Observatory. The wedges run from 170 nm (UV, shown in pink) through 9.4 nm (X-rays, shown in green), with the background image taken at visible wavelengths. Some of the wavelengths highlight features of the solar surface very well.
Update: NASA also has a beautiful video version of this image (hat-tip to sparkonit):