This is a fascinating question, and one that has already received much speculation in academic circles. What you're talking about is called a Vonn Neumann Probe.
They are a concept first postulated by Hungarian-American physicist John Von Neumann. The idea is that, with sufficient technology, we could easily make a fleet of small crafts to go out and explore interstellar space, searching for intelligent life and transmitting information back to the home planet. These probes would be able to build more probes like themselves out of raw materials, allowing the technology to arrive at a solar system and then slowly populate and explore it.
Some have theorized that there could very well be Von Neumann probes from other planets here in our solar system already, just observing us and remaining nearly impossible to detect (some even suppose they could be microscopic, built with nanotechnology). This is all speculation of course, with absolutely no supporting evidence. Interesting thoughts though!