The minimug is the standard RepRap test object. A small, shot glass sized cylinder that hopefully gets printed as a watertight part which you can toast with.
The STL file appears to have the cup laying on its side, which seems like it'd be a tough way to get it to print well. Is there a way to tell skeinforge to rotate it upright, or do I need to learn AOI to rotate it?
Water-tight is easy - don't stop until it's alcohol-tight. :)