<div id="p1" class="movers"><div id="pp1" class="moverscontent"></div></div>

<div id="demo" style="..." class="vodoo"></div>

$('#p1').draggable({
		containment: '#mainview', // äußere Grenze; auch ein DIV
		scroll: false,
		opacity: 0.35,
		cursor: 'move',
		stop: function(event, ui){ 
			// report position
			//alert("x: " + ui.position['left'] + " | y: " + ui.position['top']);
		}
}).fadeTo("fast", 0.35);
	
$('#pp1').droppable({ 
		accept: '.vodoo',
		tolerance: 'touch',
		hoverClass: 'drophover',
		drop: function(event, ui){
			// report draggable-id for droppable???
		}
});
	
$("#demo").draggable({ 
		revert: 'invalid',
		snap: true,
		snapMode: 'inner',
		snapTolerance: 20
});

<link type="text/css" href="css/ui-lightness/jquery-ui-1.7.2.custom.css" rel="stylesheet" />
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script>

<script type="text/javascript">
$(document).ready(function() {
    $('#p1').draggable({
        containment: '#mainview', // äußere Grenze; auch ein DIV
        scroll: false,
        opacity: 0.35,
        cursor: 'move',
        stop: function(event, ui) {
            // report position
            //alert("x: " + ui.position['left'] + " | y: " + ui.position['top']);
        }
    }).fadeTo("fast", 0.35);

    $('#pp1').droppable({
        accept: '.vodoo',
        tolerance: 'touch',
        hoverClass: 'drophover',
        drop: function(event, ui) {
            // DOM-Node passend verschieben
            var clone = $(event.originalTarget).clone();
            $(event.originalTarget).remove();
            
            clone.css({'left': '10px',
                       'top': '10px'});

            $(this).append(clone);
        }
    });

    $("#demo").draggable({
        revert: 'invalid',
        snap: true,
        snapMode: 'inner',
        snapTolerance: 20
    });
});
</script>

<style type="text/css">
#demo {
    background: #00f;
    width: 30px;
    height: 30px;
}
#p1 {
    width: 200px;
    height: 200px;
    background: #0f0;
}
#pp1 {
    width: 100px;
    height: 100px;
    background: #f00;
}
</style>

<div id="p1" class="movers">
    <div id="pp1" class="moverscontent"></div>
</div>

<div id="demo" class="vodoo"></div>

$(this).attr('id')