another candidate is the almost-never overloaded comma operator.

algorithm(container, /*stuff*/, &element::method)

I would be tempted to use << as a stream operator:

Notifier(listenerList) << somedata << moredata;

The side effects and behaviour of these operators are better documented and the syntax makes sense as it is similar to iostream, just my 2 cents worth...

Notifier would be a simple class like:

typedef vector<Interested*> Notifiable;

class Notifier 
{
    Notifiable * n;
public: 
    Notifier (Notifiable *n): n(n) { }
    operator<<(...) { /* overloaded code here to send data to Notifiable */ }
};

Hang on, why do we need this to be a one-liner, anyway?

Because abstractions are cool :D

Nah, personal preference, I prefer common actions like sending a message to an observer to be as simple as possible to do, so long as the implementation is abstracted away nicely and we'll documented it's all good...