I took this picture of a sundog this morning at work (Champaign, IL, on the campus of the University of Illinois). Several Facebook friends have posted similar pictures.
The scientific name for the sundog is parhelion. They are bright spots of light on either side of the sun and are caused by ice crystals, acting as tiny prisms bending (refracting) light from the Sun. Because they act like prisms, most of the time you can see several colors in the bright spots. It is fairly common to see one or both bright spots on either side of the Sun but I have rarely seen the full halo effect like this one.You can read all about sundogs on Wikipedia.