I would create document fragments with your removed li
s and then reappend them to the location you want them. In this case, I reappended them to the body:
$(function(){
var $bigList = $('#bigList'), group;
while((group = $bigList.find('li:lt(20)').remove()).length){
$('<ul/>').append(group).appendTo('body');
}
});
Live Demo is at: http://jsbin.com/ejigu/33