Best way to support many many users?

Hi,

I am setting up a web server with Postgres.

I am trying to figure out how exactly to allow multiple users to each
have their own "sandbox" without being able to interfere with other
user's data. I am also a little concerned about performance issues (I
have 256 MB RAM in my system to help with this).

Is it more efficient to start up multiple postmaster processes on
different ports, or run everything from one postmaster?

Any tips, tricks, documentation etc very greatly appreciated.

./patrick
a222(at)redrose(dot)net