Reporting on usage?

I am looking for a way to find all active members in the last X period of time. And by active, I mean someone who has made at least 1 post on the forum during the given period of time (probably 1 month).

What's the easiest way to find this information?
Answered my own question. The following MySQL query will do it.

SELECT DISTINCT username FROM `xf_post` WHERE FROM_UNIXTIME(post_date) BETWEEN '2011-07-01' AND '2011-08-01'