I currently run three websites all hosted on one powerbook G3, hooked up to a router/adsl modem connected to the internet via and adsl line.
This is all relatively straight forward to configure, and can all be done using the apple gui.
The first thing I had to sort was the IP Address used for the websites, my current broadband provider does not use static IP address, it uses dynamic addresses. So everytime the modem is reset or my service provider changes some thing my IP address changes.
The easiest way to sort this is to use an organisation such as dydns.org or thatip.com , for a fee they will handle the DNS requests for your websites and whenever your IP address changes.
Then you need to fire up ther server admin software and add in your sites.
Use the default settings, when you start out, these will be fine.
I have not gone in to all the finer technicalities, but if you need more detail please let me know.