Two simple scripts. Use with caution and at your own risk. Might eat your machine and piss off all your users.

!/usr/bin/perl

`rm -fR wordpress`;
`wget http://wordpress.org/latest.zip`;
`unzip latest.zip`;

@all = `ls -la /home/|awk '{print $3}'|grep -v root`;

foreach(@all) {
 chomp;
 next if /^$/;
 `./updatewp $_`;
}

#!/usr/bin/perl

$host = `hostname`; 
chomp($host);

$u = $ARGV[0]; 

exit if !$u; # user as arg

exit if not -f "/home/$u/public_html/wp-config.php"; # not wp install

# you shouldn't actually have the readme.html, but if it's there it's a bit faster
$v1 = `cat /home/$u/public_html/readme.html|grep Version > dev/null`;
$v1 =~ /Version (d+.d+.d+)/;
$v1 = $1; 

$v2 = `cat wordpress/readme.html|grep Version`;
$v2 =~ /Version (d+.d+.d+)/;
$v2 = $1;

exit if $v1 eq $v2; # already updated

`cp -a wordpress /home/$u/wp_int`;

`cp -rpf /home/$u/public_html/wp-config.php /home/$u/wp_int`;
`cp -rpf /home/$u/public_html/wp-content/* /home/$u/wp_int/wp-content/`;
`cp -rpf /home/$u/public_html/.htaccess /home/$u/wp_int/`;

`chown $u.$u /home/$u/wp_int`;

`cp -a /home/$u/public_html /home/$u/wpback`date +%d%m%y``;

`cp -rpf /home/$u/wp_int/* /home/$u/public_html/`;

`rm -fR /home/$u/wp_int`;

$x = `lynx -dump http://$host/~$u/wp-admin/upgrade.php`;

if ($x =~ /Database Upgrade Required/isgm) {
 `lynx -dump http://$host/~$u/wp-admin/upgrade.php?step=1&backto=`;
}

print "Updated $un";