How I can find most active users (by XP,#of posts etc)of last-week, month etc, who post on the site.

Thanks,
artist

Update: I alread know about jcwren's site. It doesn't give me the stats on 'recently active users'. this comes close, but it doesn't limit the activity time by last day or month. I am looking more along the line of what blakem has posted, (example: Last 7 days XP) for recently active users.