Version 4.0 of VirtualBox will have NAT port forwarding available in an easy to use GUI. The more fervent readers of this blog will remember this post which I described how to set this up on the command line.
Open your VirtualBox networking settings, and click the port forwarding button.
Click the little plus on the right to add your settings. You can leave out the IP - it’s optional.
You used to have to shut down your VM to change these settings. With VirtualBox 4, they can be changed while it’s running. Awesome.