When Kottke pointed to this article in New Scientist wondering what would happen if all humans disappeared tomorrow, it sucked me right in with the line, "Alien visitors coming to Earth 100,000 years hence will find no obvious signs that an advanced civilisation ever lived here."
The piece goes on to explain that there would still be paleontological evidence, but outward signs would be erased by weather and other natural processes.
Yet that's restricted to the Earth. On the Moon, our relics from Apollo landings and various robotic missions will likely remain for millions of years, unrusting and uneroded, just like our geostationary satellites and much of our miscellaneous space junk. Orbiters around other planets might still remain too, with the Pioneer and Voyager spacecraft vectoring ever further out of our solar system far away.
So yes, we could disappear from Earth with hardly a trace, but our traces would remain in space. Comforting?