So the person who created. http://www.riftstatus.net/ has created http://www.torstatus.net/ Tor Status shows the current population of each server over time. The way this site works is that it polls the STWOR.com server status page and the records that information in to the graph that we see here.
For instance the server i play on (Lord Praven) http://www.torstatus.net/lord-praven/history/7d 7 day history look like this. (You can see after midnight the server when down).
They also rank server by highest population (based on there status). So right now The Harbinger is the most popular server. And you can see it 7 day history here. http://www.torstatus.net/the-harbinger/history/7d
Nice find!