From the New Earth Online website, there comes this new tutorial for showing the current number of people browsing your website.

After recently having seen a way of showing the number of people currently visiting your site by recording IP address I thought I'd demonstrate my own way of doing it that also includes the ability to show which users online, and number of users/guests online.

They briefly explain the goal of the script and touch on another tool for WordPress that does a similar thing, but this solution would work for any site. The rest of the post is the code for the feature that uses a database table to keep track of users online (via insert/update/deletes).