I think I have accidentally done something rather stupid. Again. I ran
compiz --replace in a terminal, and I think I did something screwy to unity, because the bar at the top and the launcher is missing. I think I could live with it if:
a.) I knew how to open the home folder from the terminal;
b.) I knew how to open CCSM (Compiz Config Settings Manager) from the terminal;
but some repair for unity would be useful. I have tried
sudo apt-get update && sudo apt-get upgrade, and this: http://www.tuxgarage.com/2011/04/missing-top-and-side-panels-in-unity.html, and nothing has worked.