var $window = {
        open_in_new_tab: function(url){
                getBrowser().selectedTab = getBrowser().addTab(url);
        },

        open_in_same_tab: function(url){
                top.content.document.location = url;
        },

        open_as_popup: function(url){
                var mypopup = window.open(url,'popuppage','toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=1,width=700,height=400,left=30,top=30');
                mypopup.focus();
        },

        focus: function(obj){
                obj.focus();
        },

        click : function(aEvent,url){
                if (aEvent.button == 2){
                        this.open_as_popup(url);
                }
                else if ((aEvent.ctrlKey) || (aEvent.button == 1) || (aEvent.metaKey)){
                        this.open_in_new_tab(url);
                } 
                else {
                        this.open_in_same_tab(url);
                        this.focus(window._content);
                        
                }
        }
}

Usage:

<toolbarbutton id="myid" label="my button"  class="toolbarbutton-1" onclick="$window.click(event,'http://localhost/');" />

var mylib = {
       appendXulEl : function(parentId,nodeName,attribs){
                var elem = document.getElementById(parentId);
                var node = document.createElement(nodeName);
                for (attrib in attribs) {
                        node.setAttribute(attrib, attribs[attrib]);
                }            
                elem.appendChild(node);
        }
}

Usage:

mylib.appendXulEl('BrowserToolbarPalette', 'toolbarbutton', {'id':'MY_BUTTON_ID', 'label':'label for my button', 'tooltiptext':'button tooltip', 'class':'toolbarbutton-1', 'onclick':'alert("test")', 'context':''})