RewriteRule vb/forum.php http://www.newdomain.com/index.php [L,R=301]
RewriteRule vb/private.php http://www.newdomain.com/conversations [L,R=301]
RewriteRule vb/t([0-9]+) http://www.newdomain.com/showthread.php?t=$1 [L,R=301]
RewriteRule vb/users/([0-9]+) http://www.newdomain.com/member.php?u=$1 [L,R=301]