Select Maximum Question - Mailing list pgsql-sql

I am a SQL newbie, so hang in there with me.

I have two fields in a table, "filename" and "revision".
The table contains 3 rows where the filename is the same and
revision contains "1" "2" and "3" in each respective row.
It also contains another row for a different filename with
revision set to "1".

I want to do a select which only returns the highest revision
level for each filename, so the select will return two rows,
the first filename with revision = "3" and the second filename
with revision set to "1".

How do I do this? I imagine this is simple, but it is new to me.

Thanks.