This image taken by Thierry Legault has been making the rounds lately. That bit of a speck seen on the Sun’s lower-right limb is the shuttle on the way to perform it’s current Hubble repair mission. The spacecraft itself can be seen in much greater detail at left and another image of The Shuttle with The Hubble Space Telescope nearby can also be seen on Thierry’s website here.
A quick google search of Thierry’s name reveals that he has been at this sort of thing before. Seen below is the Shuttle and The International Space Station as seen against The Sun in 2006. These transits happen in less than a second to a ground observer, so capturing this fleeting event is no easy task.