code related to answer http://ethereum.stackexchange.com/a/5733/405

contract.sol

//deployed address is 0xdf315f7485c3a86eb692487588735f224482abe3
contract Parent{
  function fallback() internal {
    log0("Parent fallback function");
    address myAddress = this;
    log0(bytes32(myAddress));
  }

  function (){
     fallback();
  }
}

//deployed address is 0x17956ba5f4291844bc25aedb27e69bc11b5bda39
contract Child is Parent {
  function (){
    log0("child fallback function");
    address myAddress = this;
    log0(bytes32(myAddress));
    super.fallback();
  }
}

Contract2.sol

//deployed address is 0xdf315f7485c3a86eb692487588735f224482abe3
contract Parent{
  function fallback() internal {
    log1("Parent fallback",bytes32(msg.value));
    address myAddress = this;
    log0(bytes32(myAddress));
  }
  function (){
     fallback();
  }
}
//deployed address is 0x17956ba5f4291844bc25aedb27e69bc11b5bda39
contract Child is Parent {
  function (){
    log0("child fallback");
    // send zero ether to parent to call parent fallback
    address parentAddress = 0xdf315f7485c3a86eb692487588735f224482abe3;
    parentAddress.send(msg.value/2);
    super.fallback();
  }
}
// then send a transaction with 42 ETH to 0x17956ba5f4291844bc25aedb27e69bc11b5bda39
// log it then 
/*
Ethereum Console
Sandbox LOG (Child): child fallback
Sandbox LOG (Parent): Parent fallback 21
Sandbox LOG (Parent): 0xdf315f7485c3a86eb692487588735f224482abe3
Sandbox LOG (Child): Parent fallback 42
Sandbox LOG (Child): 0x17956ba5f4291844bc25aedb27e69bc11b5bda39
*/