I'm casting my vote for Virtualmin, as @ did.
You can find demo login credentials for Virtualmin here: http://www.virtualmin.com/demo
I started using Virtualmin in 2009 and grew to like it because of the expanse of features that it provides for free. There is a lot of stuff, which means that there may be a bit of a learning curve. I never read any tutorials on it, however, because even though the options may be overwhelming at first, they are self-explanatory.
, you might like the installation process for Virtualmin. It allows you to personalize the installation for the resources available on your VPS.
I used cPanel for a couple of years, but when I found out that Virtualmin could restore hosting accounts from cPanel backups, I moved all my sites to use Virtualmin as the control panel. (I did end up switching back to cPanel, though, especially since I've become a cPanel certified technician. cPanel has a method to their madness that I've become fond of.)
It's actually been quite a while since I've used Virtualmin, but if you want some more personalized input about it from me, feel free to PM me.