Hello, (so many so little time)
Without a doubt Hubble Deep Field (not necessarily an object but...) - the first time I saw this photo, with the scale/field of view listed - something like a dime at 75 feet, my jaw dropped. Galaxy upon galaxy in an area the size of a pin-hole. WHEW.

I'm beating Dan to the punch on this one because I know this is his one of his favorites as well : (Pleiades)
http://www.astropix.com/HTML/SHOWCASE/M45.HTM
On a seperate note,
Just scanning the sky with the naked eye Saturday night/Sunday morning
was a real treat. Too often we are consumed with a specific area, object, etc.. I felt a real sense of appreciation and wonder just looking around.
Part of me became sadden by the fact that I will be lucky (in my lifetime)to see a man set foot on another planet. There is soooo much out there, it seems ludicrous that we are not spending more time and money on space exploration. I also began to think about galaxies, stars, etc. who's light has not even reached the earth - what lies beyond our observable universe????
Have a good day, see ya -VINCE