If you want to understand what's going on in the sky, there are lots of ways to do it. You can, for example, look around for specific examples of objects -- supernovae, black holes, spiral galaxies -- and examine them. Or, you can take a survey of the sky, looking everywhere, and take a census of objects. That gives you a pretty good idea of how many objects are out there, and how many of each kind.
Surveys of the sky tend to revolutionize our thinking about astronomy. When you get large samples of vast stretches of sky, you get a feel for what's going on, and sometimes that overall view can be very powerful.
The UK Infrared Telescope just released a new survey, the deepest and largest infrared survey of the sky ever made. IR light is tremendously useful in astronomy; it can pas through gas and dust pretty well, revealing objects otherwise hidden under a thick blanket of obscuring material.
The UKIRT Infrared Deep Sky Survey was started back in 2005, and looks at the near infrared, the light just outside the eye's sensitivity. It does so with exquisite sensitivity and depth; producing a wealth of data as well as beautiful imagery. They have found the coolest (literally!) brown dwarf yet -- a star that is too small to sustain fusion in its core, dooming it to slowly cool with time as its internal heat is released.
Besides revealing previously unknown objects, surveys can give us details of familiar ones as well, like in the Ring Nebula picture at the top of this post. That's one of the most famous objects in all the sky, a dying star shedding layers of gas which light up as they collide and are heated by the central star. It's visible in small telescopes and has been photographed countless times. But a deep, wide survey unveils the far outer halo of the nebula, gas flung out long ago in the earliest stages of the star's death. This will tell astronomers details about what happens just at the point when stars like the Sun begin to shuffle off their mortal coil.
And the UKIRT survey isn't even done! When it's complete, in 2012, they will have detected 100 million galaxies, which is phenomenal (imagine having to catalog all of them...), and revealed many hidden treasures in our own. Surveys like this are extremely powerful tools in an astronomer's kit, and will be mined for data for decades to come.