Amazon EC2 multiple private IP addresses per instance
Unfortunately this is still the case. Quoting from the Amazon EC2 Elastic IP Addresses - FAQ:
Can an instance have more than one Elastic IP or Public IP?
Today, an instance can only have one Internet routable IP address. If an Elastic IP is mapped to an instance its existing Public IP address mapping is removed.
Afaik, it's still not possible.
Some people run vserver or UML on an ec2 instance. You could set up various environments in there and then port forward from the host, etc. but that seems overcomplicated (IMHO).