Sure there is. With the redesign of the front page alot of the detail that was on the bottom of the main page was removed. But if you look at the bottom of this page www.aquariumadvice.com/index.php
you will see the Who's Online block you have come to love.
If you want a summary you can also visit http://www.aquariumadvice.com/viewonline.php
And it will show you a bit more detail as to where they are at in relationship to the site.
EDIT: Chand the link above to reflect the now current correct file path