I host a website for an organization. I'd like it's members to be able to create forwarding e-mail aliases. Is there an application or tool that would allow people to create their own alias?
there is currently no API for that..... http://wiki.dreamhost.com/API/Mail_commands
Creating alias should be administrator's job. If you are using DH email server, try to log into webmail.yourdomain.com. If you are using gmail, try to log in as administrator.