current user,login,logout in sidebar

Here’s the code that displays that info in the admin area of your site:
<div id="user_info"><p><?php printf(__('Howdy, <a href="%1$s">%2$s</a>!'), 'profile.php', $user_identity) ?> | <a href="<?php echo get_option('siteurl'); ?>/wp-login.php?action=logout" title="<?php _e('Log Out') ?>"><?php _e('Log Out'); ?></a> | <?php _e('<a href="http://codex.wordpress.org/">Help</a>') ?> | <?php _e('<a href="http://wordpress.org/support/">Forums</a>') ?></p></div>

You’ll need to put in some checks, probably include a few pages from the admin area, but that’s a start.