Depends on what you mean. The farthest away probes, Voyager 1 and 2, have left the solar system proper, but we still haven't sent probes to all of the significant planetary bodies in the solar system (e.g. Pluto). No manned spacecraft has been to any other object in our solar system besides the Moon. Our incomplete exploration of our own solar system is largely due to the amount of money that the United States, European Union, and Russia (and formerly the Soviet Union) spend on their respective space programs, and the risks associated with manned space flight to distant objects (and the great expense associated with trying to make it safer). The distance we've been able to send probes owes to our limited technology in building spacecraft.