I also do port mapping to let clients view my VMs... I always use bridged connections as mentioned above.
For the router, you might want to take a look at CoyoteLinux or Mitel's (a.k.a. e-smith) firewall distribution. Stick a coyotelinux floppy into an old PC with two NICs and you have a router. Mitel is a RedHat derivate tuned for security and ease of maintenance. Both have been good to me.
