[Fernando Tellado]

You may do it by .htaccess … 

From www to no-www

Options +FollowSymLinks

RewriteEngine on

RewriteCond %{HTTP_HOST} .

RewriteCond %{HTTP_HOST} !^www.myforums.com.com

RewriteRule (.*) myforums.com/$1 [R=301,L]

and the opposite … 

Options +FollowSymLinks

RewriteEngine on

RewriteCond %{HTTP_HOST} ^myforums.com [NC]

RewriteRule ^(.*)$ http://www.myforums.com/$1 [L,R=301]