Where can I get a Postgres 9.0 package?
Solution 1:
I would go with this PPA, maintained by Martin Pitt.
https://launchpad.net/~pitti/+archive/postgresql
(Martin Pitt is also the one maintaining the official Debian- and Ubuntu PostgreSQL packages.)
Solution 2:
Please check http://wiki.postgresql.org/wiki/Apt Its up since some time and offering direct packages.