Ceiling Light Help - Quiz - 3 sets of wires
It`s just like you said: one wire is to the switch (the one with the black going to the fixture), and the other two wires are power in and power out to the next segment of the circuit. I don`t know why you want to find out where the power is feeding to, but the only way to do this is to map out the circuit in question; find out everything thats on this circuit. When you do that, you`ll most likely see where the wire leads to, as it will probably be as close to the this ceiling box as possible.
Anyways, to cover the ceiling box up, you can buy white ceiling box covers that are very easy to install and look pretty good, as well.