var t = $('h1').text();
$('h1').html('<span>'+t.substring(0,1)+'</span>'+t.substring(1));
EDIT: , ( , ).
$('#main-nav li').each(function() {
wrap_first_character(this, $('<span>'));
});
function wrap_first_character(ele, tag) {
var t = $(ele).text();
$(ele).append(tag.html(t.substring(0,1))).append(t.substring(1));
}