Counting comments

Hello

I am currently running a competition on my blog where the five people to post the most (approved) comments in the month wins one of 5 stays in a Hyatt hotel anywhere in the world. ( http://www.aluxurytravelblog.com/2009/04/30/win-a-stay-at-any-hyatt-in-the-world/ )

Is there any way I can easily count how many each participant has posted rather than just laboriously going through by hand?

Thanks!

Paul