Timespan / interval calculations?

I'm using PostgreSQL 6.5. I have a table with a timestamp field. I
want to extract all rows with a timestamp less then an hour ago. I've
tried several things, but nothing seem to work. How should it be
done?

I've tried

select * from syslog
where stamp between timestamp('now') - interval('1 hour') and 'now';

select * from syslog
where stamp between timestamp('now') - timestamp('1 hour') and 'now';

but none of these works.

It seem to be something wrong with the interval and timespan types.

pere=> select interval('1 hour');
ERROR: parser: parse error at or near "("
pere=> select timespan('1 hour');
ERROR: Function 'timespan(unknown)' does not exist
Unable to identify a function which satisfies the given argument types
You will have to retype your query using explicit typecasts
pere=>

Should this work, or is it my mistake?

(I'm not on the mailing list, please copy replies to me. :-)
--
##> Petter Reinholdtsen <## | pere(at)td(dot)org(dot)uit(dot)no