Here are some facts on a few strange and interesting items and events pictured by the Hubble...
Black Holes
Black holes occur after the death of a star, or more specifically, after a supernova. If the core of the star is massive enough, it will collapse into itself. It becomes a powerful vacuum that is powerful enough to compress even neutrons. As the core gets smaller, the surface gravity become greater and the velocity needed for anything to escape the pull becomes exponentially greater. Eventually, it becomes so powerful that even light itself cannot escape it. This is where black holes get their names. When light cannot escape it, the mass is not part of the visible universe. 
There is an invisible sphere on the outside of the black hole. This is the boundary called the event horizon or point of no return where the black hole's gravity has any power. The event horizon is actually only a few miles in diameter. What lies within a black hole is unknown. A theory is that the collapsing core continues to shrink until it becomes an infinitely small point of infinite density known as a singularity. But, it is only a theory... We will probably never know what exists inside a black hole.
Pictured to the right is a nearby galaxy that seems to have some kind of x-ray signal source in the middle. It is only speculation, but many scientists believe that a supermassive black hole exists in the center... just like in our own galaxy.
Quasars
Quassi-stellar radio sources, or quasars, are stars that are hundreds of times brighter than many stars or galaxies. They emit energy in all different forms such as light waves, x-ray waves, infrared waves, and even radio waves. They are hard to measure in size because of the varying brightnesses but some have placed the size of quasars as being about the same size of the Milky Way.
All quasars detected by the Hubble are very distant. The quasar PKS 2000-330, for example, is at a distance of around 13 billion light years (the distance light travels in one year at 186,000 miles per second). This means that we are seeing it as it was close to the time when we believe the universe was born.
Supernovas
A supernova denotes the end of the life of a star. When a star uses up all of it's energy, it compresses and explodes. Supernova are among the most powerful events in the known universe and occur once every 200 to 300 years in any given galaxy. They can be broken down into two different categories: Type I and Type II. Type I supernovas occur in a binary star system (two stars next to each other). When the smaller star attracts too much matter from a larger star, it can no longer support itself. It then explodes.
Type II supernovas occur when a star that is larger than our own sun dies. They are more common than Type I supernova and release much more energy, but not in the form of visible light.
Pictured to the right is the doomed star Eta Carinae. At this point, the star is ejecting massive amounts of matter and energy. The star inside is extremely hot. The hint of blue light shows where the star is located and how small it really is. Eta Carinae is set to go supernova at any time... and it will be a spectacular sight.