temporary tables

Since I cannot return a set of values (namely rows from a table) from a
function, I thought I could create a temporary table where I could place
the resulting information.

Unfortunately I have a big problem. If I create this table and run the
same procedure again (during the same session) I'll get a message saying
the table already exists, but there's no way I can drop this table from
plpgsql. Is there a way I can implement this?

Thanx.