Your light cone is the portion of the universe that you could had influenced. It grows at the the speed of light from the moment you are born (okay, that’s fudging things, but bear with the assumption.) Matt Web has a tool to let you generate your light cone, in terms of nearby stars, as an RSS feed.
Remember, do not step outside your light cone, that will anger the happy fun Eschaton, and I don’t mean Mr. Atrios.
He’s also listed the Python source for this so you don’t have to hammer his host.
