Use jquery's delay()
$("div").each(function(index){
var self = $(this);
self.not(':animated').css(
{'opacity': 0.8}
).delay(700 * index)
.effect(
"scale",
{
origin:['middle','center'],
from:{width:self.width()+20,height:self.height()+20},
percent: 100,
direction: 'both',
easing: "linear"
},
700,
function(){
$(this).animate({"opacity": 1})
});
}, 100);
});