Customer

$proxy = new SoapClient('http://magentohost/api/soap/?wsdl');

$newCustomer = array(
    'firstname'  => 'First',
    'lastname'   => 'Last',
    'email'      => 'test@example.com',
    //for my version of magento (1.3.2.4) you SHOULD NOT
    // hash the password, as in:
    // 'password_hash' => 'password'
    'password_hash'   => md5('password'),
    // password hash can be either regular or salted md5:
    // $hash = md5($password);
    // $hash = md5($salt.$password).':'.$salt;
    // both variants are valid
    'store_id'   => 0,
    'website_id' => 0
);

$newCustomerId = $proxy->call($sessionId, 'customer.create', array($newCustomer));

// Get new customer info
var_dump($proxy->call($sessionId, 'customer.info', $newCustomerId));


// Update customer
$update = array('firstname'=>'Changed Firstname');
$proxy->call($sessionId, 'customer.update', array($newCustomerId, $update));

var_dump($proxy->call($sessionId, 'customer.info', $newCustomerId));

// Delete customer
$proxy->call($sessionId, 'customer.delete', $newCustomerId);