One minor edit - the code snippet left two trailing slashes on the rewritten URL:
<IfModule rewrite_module>
Options Indexes FollowSymLinks +IncludesNOEXEC
RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.mydomain\.org$ [NC]
RewriteRule ^/?(.*)$ http://www.mydomain.org/$1 [L,R=301]
</IfModule>
The added /? fixes that.