There are many. CentOS Web Panel, Virtualmin, DirectAdmin, Interworx, and many others. I use Virtualmin on my own stuff. It has a FOSS version that works well.

There are many. CentOS Web Panel, Virtualmin, DirectAdmin, Interworx, and many others. I use Virtualmin on my own stuff. It has a FOSS version that works well. But it's no cPanel. The interface and general paradigms leave a lot to be desired. But it works. The problem isn't variety, it's user base. All the Big Hosts are using cPanel, migrating away from it is a pain. There's also Plesk, but let's face it. Nobody likes Plesk.