VirtualBox - Let Host-Only mode access the internet

In an earlier post I described networking modes in VirtualBox. Combining those modes you'll get some kind of swiss knife in realizing somehow exotic networking modes in your VMs.
What if you want your VM that is configured for Host-Only mode access the internet?
Port forwarding using NAT is an option. But for me that sounded to complicated. I had the following requirements:

1. The host should be able to access services like Apache or GlassFish on the guests (the virtual machine)
2. The guests should be able to access the outside world (intranet/internet)
3. The guests should be able to talk to each other using fixed IP adresses
4. The host should be able to talk to the guests using fixed IP adresses

A working solution for these requirements is described in this blog article.