hiding DIV when clicking away from it

You should use stopPropagation:

$(body).click(function(e)
{
   $('#optionsMenu').slideUp('fast');
});
$('#optionsMenu').click(function(e)
{
   e.stopPropagation();
});

You could use on(), perhaps:

$('body').on('click', function(e){
    if ($(e.target).not('#optionsMenu')){
        $('#optionsMenu').slideUp('fast');
    }
});

The above not yet tested, but should, I think work.