database permissions:how to create read only user for db

Hello all.

Please help,
are there any way to set some (ex. deny creating tables) privileges on database (not for databases objects)?

I want crant full access to one user (let say "adminuser" for database "testdb") and make some others (read only)
users,
who can read only (do SELECT from "testdb" tables), but not CREATE tables or some database objects.

As I know CRANT command allows only set privileges for database objects but not for databases.

So, can I realize this using Postgres 7.1,
or it's not possible at all?

Thanks in advance.
/lexx/