The research physics that has been done since people started accelerating the atom in early 20th century has altered the world -- it was that research in the 1930's that first split the atom, and lead to the double edged sword of nuclear power and nuclear holocaust.  Of course, what we do with new-found knowledge can be either beneficial or destructive.

Currently, these devices have led us to confirm aspects of the Theory of Relativity and Quantum Mechanics; they have led to the understanding of ever more fundamental particles that compose the matter of the Universe, and eventually, may lead us to fully understanding how the Universe works by showing us how to unify the Fundamental Forces.  The practical developments are expansive and unknown --anti-gravity boots, time travel, new sources of energy -- it starts to sound like science fiction.

I think we have not quite exhausted all of the uses of particle accelorators.  As we develop more science, we will be able to take what we have and develop new theories and inventions to help us do more.  I am not sure time travel is possible, but what about space travel?

I think the major one that perhaps most people are familiar with is the way that particle accelerators benefit the medical profession through a wide range of uses, most common in X-rays and radiotherapy. #2 makes an interesting point that really particle accelerators have been around for so long that we don't actually think of them as being "new" so much, though of course the uses to which they are being put are constantly changing as technology develops.

I would argue that large particle colliders really don't do much to benefit society in tangible ways.  However, people who advocate spending public money on large particle colliders argue that the colliders end up helping scientists discover things that will have a great deal of usefulness for society.  If you follow the link below, you can look at a series of brochures that tell how large particle accelerators can help with everything from health care devices to devices for the creation of more "green" energy.

http://www.aps.anl.gov/Science/APS_and_You/

Particle accelerators, after the Large Hadron Collider built by CERN came online, seem to have become familiar to almost everyone and have gained notoriety as devices that could bring the universe to an end.

No one seems to remember what a particle accelerator actually is and how for a long time now they have been part of almost  everyone’s life.

A particle accelerator is a device that using electromagnetic fields can propel atomic and sub-atomic particles to high velocities while ensuring that their path can be well-controlled. The cathode ray tube that was an essential component of almost all television sets built until a few years back is a particle accelerator. More powerful particle accelerators are used to generate X-rays and are used in almost every hospital for purposes ranging from imaging to anti-cancer therapy involving radiotherapy.

Particle accelerators are also widely used in industrial processes, some examples of which are in the manufacture of integrated circuits and in ion implantation. They also find wide applications in biomedical and industrial research.