Re: *** How can I install two postgresqls in the same machine? *****

We've also wrapped the psql command with our own script which takes a
database name as a parameter, determines what IP & port to connect to
and also determines the version of postgres running so the proper psql
client is invoked.  I don't know if it's a must but you'll be warned if
you try to connect to a 8.1 using a 7.4 client.

Care to share that script or at least show us how it works?  This sounds like a great way to gradually upgrade applications to new database versions, especially when you have many clients on a machine and upgrade only some of them at a time.

Thanks!
Aaron