Restrict access

Hi,

I have created a database and imported a lot of data. I would like to
share this database with other people but they should not be able to
change anything. That is, they should only be allowed to use the
SELECT command.

If I create a user, this user can access the database and see the
names of all tables. I can now GRANT this user permission to use
SELECT on all tables. Apparently, this seems to solve the problem.
However, I have noticed that if people access the database using my
username (i.e. by typing "psql foo -u" and the providing my username)
they get full access. I have tried to disable this by "ALTER USER
username WITH PASSWORD 'password'" but that doesn't help. You still
don't need to supply any password.

I have used Google for several hours with coming even near a solution
so any help is appreaciated!

--
Michael Knudsen