Astronomers like to make cool names for boundaries in outer space. If you cross the point of no return near a blackhole, it's called the event horizon. However, when you leave the heliosphere of our Sun, it's called the termination shock.
The heliosphere is a sphere surrounding the solar system in which the solar wind, electronically charged particles emitted at high speeds by our Sun, slows to subsonic speeds. The solar wind travels at supersonic speeds when it is emitted and eventually slows as it "pushes" against the interstellar medium of plasma, neutral gas, and dust. This boundary is not fixed, meaning it can change depending on certain variables.
Since the heliosphere moves back and forth, it is estimated that Voyager 2 will cross the termination shock twice: once in the next month or two and again in the middle of 2008. The spacecraft is now in the outer heliosphere, beyond which lies galactic space.
The spacecrafts next big step will be the heliopause: the boundary where the solar wind comes to a complete halt.
This probe was launched nearly 5 years before I was born, yet still is running strong. We can't build a moon base in 2007 but we could send a probe hurtling into space that is functional for a full 30 years? It's very frustrating to see that we have to build back our knowledge back to what it was 30 years ago. Of course this makes the statement, "They don't make 'em like they used," an accurate statement concerning spacecraft.