This CodeLet will store user's login history and creates a block. Admin can place this block on user pages or on pages. Future ammendments to this code will allow to use the stored login details to be displayed using a theme function.
This CodeLet will be submitted to Drupal.org community soon.

Drupal: Last Login details | Drupal Developer
CodeLet
<?php
/**
 * @file
 *
 * Logs user's logins and display last login details
 *
 * DrupalD <DrupalD@twitter>
 */


/**
 * Implementation of hook_user
 *
 * @param $op
 * @param $edit
 * @param $account
 * @param $category
 * DrupalD <DrupalD@twitter>
 */
function last_login_user($op, &$edit, &$account, $category = NULL) {
    global
$user;
    switch (
$op) {
        case
'login':
        case
'register':
           
db_query('INSERT INTO {last_login VALUES(id, %d, %d)', $user->uid, time('now'));
            break;
    }
}

/**
 * Implementation of hook_block
 *
 * @param unknown_type $op
 * @param unknown_type $delta
 * @param unknown_type $edit
 * DrupalD <DrupalD@twitter>
 */
function last_login_block($op = 'list', $delta = 0, $edit = array()) {
    if (
$op == 'list') {
           
$blocks[0] = array(
             
'info' => t('Last login'),
             
'status' => 1,
             
'weight' => 0,
             
'region' => 'right',
            );
            return
$blocks;
    }
    if (
$op == 'view') {
            switch (
$delta) {
                case
0:
                   
$output = _get_last_login();
                    echo
$output;
                   
$block = array(
                     
'subject' => t("Last login"),
                     
'content' => $output,
                    );
                    break;
            }
         return
$block;
    }
}

/**
 * _get_last_login
 *
 * Get last login details of the user
 * DrupalD <DrupalD@twitter>
 */
function _get_last_login() {
    global
$user;
   
$sn__last_login = db_result(db_query('SELECT last_logged FROM {last_login} WHERE uid = %d ORDER BY id DESC LIMIT 1, 1', $user->uid));
    if (empty(
$sn__last_login)) {
       
$sn__last_login = db_result(db_query('SELECT last_logged FROM {last_login} WHERE uid = %d ORDER BY id DESC LIMIT 0, 1', $user->uid));
    }
    if (!empty(
$sn__last_login)) {
     
$output = t('Last login at @time on @date', array('@time' => format_date($sn__last_login, 'custom', 'h:m A T'), '@date' => format_date($sn__last_login, 'custom','m/d/Y')));
    }
    else {
       
$output = t('Last login details not available');
    }
    return
$output;
}
?>
Info file details
name = Last login details
description = Shows user's last login time stamp.
core = 6.x
package = Login
Install file details
<?php
/**
 * @file
 *
 * Schema file for Last login
 *
 * DrupalD <DrupalD@twitter>
 */


/**
 * Implementation of hook_install
 *
 * DrupalD <DrupalD@twitter>
 */
function last_login_install() {
 
drupal_install_schema('last_login');
}


/**
 * Implemetation of hook_uninstall
 *
 * DrupalD <DrupalD@twitter>
 */
function last_login_uninstall() {
 
drupal_uninstall_schema('last_login');
}


/**
 * Implemeantation of hook_schema
 *
 * DrupalD <DrupalD@twitter>
 */
function last_login_schema() {
 
$schema = array();
 
$schema['last_login'] = array(
   
'fields' => array(
     
'id' => array(
       
'type' => 'serial',
       
'length' => 11,
       
'not null' => TRUE,
      ),
     
     
'uid' => array(
       
'type' => 'int',
       
'length' => 11,
       
'not null' => TRUE,
      ),
     
     
'last_logged' => array(
       
'type' => 'int',
       
'length' => 11,
       
'not null' => TRUE,
      ),
     
    ),
   
'primary key' => array('id'),
  );
 
  return
$schema;
}
?>
Submitted by DrupalD on