Try this:
Code:
NameVirtualHost aaa.bbb.ccc.ddd:80
NameVirtualHost aaa.bbb.ccc.ddd:8080
# where aaa.bbb.ccc.ddd is the IP address of your server
<VirtualHost aaa.bbb.ccc.ddd:80>
ServerName mydomain1.com
DocumentRoot /path/to/doc_root_1
</VirtualHost>
<VirtualHost aaa.bbb.ccc.ddd:8080>
ServerName mydomain1.com
DocumentRoot /path/to/doc_root_2
</VirtualHost>
<VirtualHost aaa.bbb.ccc.ddd:80>
ServerName mydomain2.com
DocumentRoot /path/to/doc_root_2
</VirtualHost>
You will need ServerAlias entries in each VirtualHost block for any other host names that they should respond to. Unaliased host names will use the first (default) VirtualHost entry.