Ajax - TinyMCE Saving

 To get the content of the editor of TinyMCE, use

function save(){

    var mce = tinyMCE.get('content');

    alert(mce.getContent());

}

For initializing the editor, use:
tinyMCE.init({
        // General options
        mode : "textareas",
        theme : "advanced",
        plugins : "spellchecker,pagebreak,style,layer,table,save,advhr,advimage,advlink,emotions,iespell,inlinepopups,insertdatetime,preview,media,searchreplace,print,contextmenu,paste,directionality,fullscreen,noneditable,visualchars,nonbreaking,xhtmlxtras,template",

        // Theme options
        theme_advanced_buttons1 : "save,newdocument,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,|,styleselect,formatselect,fontselect,fontsizeselect",
        theme_advanced_buttons2 : "cut,copy,paste,pastetext,pasteword,|,search,replace,|,bullist,numlist,|,outdent,indent,blockquote,|,undo,redo,|,link,unlink,anchor,image,cleanup,help,code,|,insertdate,inserttime,preview,|,forecolor,backcolor",
            
        theme_advanced_toolbar_location : "top",
        theme_advanced_toolbar_align : "left",
        theme_advanced_statusbar_location : "bottom",
        theme_advanced_resizing : true,

        // Skin options
        skin : "o2k7",
        skin_variant : "silver",       
});

To send the content to the server, use:
function send(){
    var data = tinyMCE.get('content').getContent();
    var ajax = new XMLHttpRequest();
    ajax.open('POST','hello.php',false);
    ajax.setRequestHeader('Content-type','application/x-www-form-urlencoded');
    ajax.send('data='+data);
}

Ajax - TinyMCE Saving