Look on the main "Forum" page. towards the bottom before all that admistrative junk I have down there you'll see a block that reads;

Who is Online
Our users have posted a total of 12794 articles
We have 1002 registered users
In total there are 26 users online :: 4 Registered, 0 Hidden and 22 Guests

That stuff is autoamtically updated so it stays accurate.