current_timestamp does NOT return the same value each time and it is the documented and prefered way to do this:
create function foo() returns timestamptz as 'begin return current_timestamp; end;' language 'plpgsql';
CREATE FUNCTION
openacs46=# select foo();
foo
-------------------------------
2003-06-19 00:32:23.515002+00
(1 row)
openacs46=# select foo();
foo
-------------------------------
2003-06-19 00:32:25.632249+00
(1 row)
openacs46=# select foo();
foo
-------------------------------
2003-06-19 00:32:31.894221+00
(1 row)
