Maybe it will be useful for someone.
The only way to have two sidebars I found at the moment is:

• Create 2 new classes like:
  

  class SidebarOne extends Page {
     static $db = array();
     static $has_one= array(
        "SideBar" => "WidgetArea",
     );
  class SidebarTwo extends Page {
     static $db = array();
     static $has_one= array(
        "SideBar" => "WidgetArea",
     );

  
  
• Then you can get them with (put this in Page_Controller):
  

  /*** Get Widgets to show 'em on a page*/
  public function GetSidebarOne(){
  return DataObject::get_one("SidebarOne");
  }
  public function GetSidebarTwo(){
  return DataObject::get_one("SidebarTwo");
  }

  
  
• In templates use smth like:
  

  <% if GetSidebarOne %>
     <% control GetSidebarOne %>
        $SideBar
     <% end_control %>
  <% end_if %>

  
  

Not sure if it is the best way, but nevertheless.