Track Users Online with Sessions?

Since I'm on the topic of sesions, I've seen a few examples of tracking
online users using a mysql table and inserting the session and
timestamp and checking it at period to remove it from the list after
expiration time but is there a simpler way? Is there a way to count
how many active sessions there are open at one time? I don't care to
see user info but would like to at least know how many people are
online. I guess getting logged in users and guests would require using
a table or something. Is there any information on how to do this?
Thanks
Received on Mon May 1 02:45:21 2006