Event is a little library built on top of boost::signal and boost::mpl that allows the user to declare in a simple way an object that can emit events and allow connection of (type-safe) callbacks as event handler to them. Usage is pretty straightforward, as shown in test/hello.cc:

#include <iostream>
#include "event.h"

enum { HELLO /* event type */ };

using namespace CyberzOrg::Event;

struct HelloEmitter  
 : Emitter<
  Event<HELLO, void (const std::string &)>
 >
{ };

void callback(const std::string &s) {  
 std::cout << "Event HELLO: " << s << std::endl;
}

int main() {  
 HelloEmitter hello;

 // preferred syntax (useful if event emitter has the event table depending on itself,
 // in such case getSignal method is not directly visible).
 getSignal<HELLO>(hello).connect(callback); // connect signal handler (callback)
 getSignal<HELLO>(hello)("hello world"); // fire signal

 // easy syntax
 hello.getSignal<HELLO>().connect(callback); // connect signal handler (callback)
 hello.getSignal<HELLO>()("hello world"); // fire signal
}

You can look at sources or download a tarball. Any feedback is well accepted.