Mark

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

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_URI} !(.*)/$
RewriteRule ^(.*[^/])$ $1/ [L,R=301]