Events in C++

Hi,

I'm looking for some help on how to best implement an observer pattern in
C++. I have an object that several objects will register with, and on
each event, all the objects are notified.
Any hints about existing libraries/code I could use for this are also
welcome!
Here is a simple example of the code I'm using now:

class ExampleListener
{
public:
  virtual ~ExampleListener() { }
  virtual void onReceive(ExampleData*) = 0;
};

class ExampleProcessor : public ExampleListener
{
  private:
    vector<ExampleListener*> todo;
  public:
    virtual void onData(ExampleData* data)
    {
    // todo.push_back(data); would cause segfaults later on
        todo.push_back( new ExampleData(data) );
    }
   //...
};

class ExampleGenerator
{
  private:
    vector<ExampleListener*> listeners;
    void fire(ExampleData* d)
    {
      for (it = listeners.begin(); it != listeners.end(); it++)
        (*it)->onData(d);
    }
  public:
    void addListener(ExampleListener* l)
    {
      listeners.push_back(l);
    }
    void run()
    {
      //...
      fire(x); delete x;
      //..
      fire(y); delete y;
      //..
    }
};

int main()
{
   ExampleProcessor a, b;
   ExampleGenerator g;

   g.addListener(a);
   g.addListener(b);

   g.run();
}

In my situation, ExampleProcessor typically either stores the data, or
does nothing with it. I don't like the fact that it has to do the copy
itself, it's just too easy to forget!
I though about passing an auto_ptr like this: virtual void onData
(auto_ptr<ExampleData> data) But if I do that, I have to copy the
data for each listener, while typically, only 1 listener will need to
store it. Perhaps some smarter version of auto_ptr is handy here? Any
comments and hints on how to do this best are more than welcome!

greetings,
Wim