Options +FollowSymLinks
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} robots.txt$ [NC]
RewriteRule ^([^/]+) $1 [L]

RewriteCond %{HTTP_HOST} ^site\.com
RewriteRule ^(.*)$ http://site.org/$1 [R=301,L]
RewriteCond %{HTTP_HOST} ^www.site\.com
RewriteRule ^(.*)$ http://site.org/$1 [R=301,L]