I believe the configuration for that is in the apache2.conf file. It's been a while since I messed with apache. Look for "root directory".
As for letting FTP into that directory, the trick is to mount that directory on a loopback interface so that it is within your jailed zone (you're probably using chroot jails with VSFTP). In fstab, it should look something like
/var/www/html /home/intranet ext3 defaults,loop 0 0