Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

uses
   Clipbrd;

 procedure ListBoxToClipboard(ListBox: TListBox;
   BufferSize: Integer;
   CopyAll: Boolean);
 var
   Buffer: PChar;
   Size: Integer;
   Ptr: PChar;
   I: Integer;
   Line: string[255];
   Count: Integer;
 begin
   if not Assigned(ListBox) then
     Exit;

   GetMem(Buffer, BufferSize);
   Ptr   := Buffer;
   Count := 0;
   for I := 0 to ListBox.Items.Count - 1 do
   begin
     Line := ListBox.Items.strings[I];
     if not CopyAll and ListBox.MultiSelect and (not ListBox.Selected[I]) then
       Continue;
     { Check buffer overflow }
     Count := Count + Length(Line) + 3;
     if Count = BufferSize then
       Break;
     { Append to buffer }
     Move(Line[1], Ptr^, Length(Line));
     Ptr    := Ptr + Length(Line);
     Ptr[0] := #13;
     Ptr[1] := #10;
     Ptr    := Ptr + 2;
   end;
   Ptr[0] := #0;
   ClipBoard.SetTextBuf(Buffer);
   FreeMem(Buffer, BufferSize);
 end;

 procedure ClipboardToListBox(ListBox: TListbox);
 begin
   if not Assigned(ListBox) then
     Exit;

   if not Clipboard.HasFormat(CF_TEXT) then
     Exit;

   Listbox.Items.Text := Clipboard.AsText;
 end;


 //Copy all items from Listbox1 to the clipboard 
procedure TForm1.Button1Click(Sender: TObject);
 begin
   ListBoxToClipboard(ListBox1, 1024, True);
 end;

 //Paste items in clipboard to Listbox2 
procedure TForm1.Button2Click(Sender: TObject);
 begin
   ClipboardToListBox(Listbox2);
 end;

 //Copy only selected items from Listbox1 to the clipboard 
procedure TForm1.Button3Click(Sender: TObject);
 begin
   ListBoxToClipboard(Listbox1, 1024, False);
 end;