Back flips isn't the word for it, but some routing device in front of the web server that can read the in coming site and bounce it correctly is the way to do it.
How about using a basic web page when you come in on port eighty that reads the URL you're coming in on and bounces you to a different site based on it... Something like this for default.asp (you would put the specific port at the end (https://AlternativesOnline.com:443)...
'Redirect the user
Response.Buffer = true
select case lcase(request("server_Name"))
case "www.ixchel.org", "ixchel.org"
case "gswitz.com", "www.gswitz.com"
case "reedsquarefoundation.org", "www.reedsquarefoundation.org"
case "www.partnersinservice.org", "partnersinservice.org"
Click <a href="alternatives/default.asp">here</a> to visit Alternatives Online's site.