My astronomy instructor took a picture of Jupiter from our observatory a few days ago, I had him send me the image to see if I could digitally enhance it and get a better picture. The image on the left is the original, the one on the right is the enhanced picture - click to get the full sized image (damn forum size limitations...)
I believe the image was taken with the 20mm eyepiece with a 2x Barlow extension, which is roughly 30X magnification. The three moons shown in orbit are Ganymede (I think that's the top left moon), Io, and Europa (believe Europa is the bottom right moon). Callisto, the fourth Gallilean moon, is not in the image - it would be in the upper-left corner of the picture if the image was expanded.
Interesting fact: Europa has a frozen surface, but is believed to have an ocean of liquid water roughly 100 kilometers deep below the icy terrain. When the voyager probe went past jupiter initially, images allowed observation of the surface ice of europa "splitting", and afterwards liquid water would fill the gap and freeze over. For colonizing the outer parts of the solar system, Europa seems to be our best bet for obtaining water without having to take it with us.