“NASA’s Voyager 1 spacecraft has entered the solar system’s final frontier, a vast, turbulent expanse where the Sun’s influence ends and the solar wind crashes into the thin gas between stars. The intrepid twin Voyager spacecraft, launched about two weeks apart in the summer of 1977 and now heading out of the solar system, continue making history. ” – Quoted from NASA’s Voyager site

http://voyager.jpl.nasa.gov/

“Still operating in remote, cold and dark conditions billions of miles from the sun, the Voyager 1 and 2 spacecraft owe their longevity to radioisotope thermoelectric generators which produce electricity from the heat generated by the natural decay of plutonium.”

“Voyager 1 has already passed the termination shock, where the million-mile-per-hour solar wind abruptly slows and becomes denser and hotter as it presses against interstellar gas. It was expected the wind beyond the shock would slow to a few hundred thousand miles per hour. But the Voyager scientists were surprised to find that the speed was much less, and at times the wind appeared to be flowing back inward toward the sun.”

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http://www.physorg.com/news6788.html

You may also remember these craft as the central plot device used in Star Trek 1 (the motion picture) when a fictional Voyager 6 (calling itself V’ger in corrupted English) returns to earth in 2271 in a vain attempt to find ‘the Creator’ with a need to destroy the ‘carbon-based units’ infesting the Enterprise.
The coolest thing of course, is the Golden Record the ships carried.