Webmin is a free web hosting control panel compatible with most Linux distributions. To install on CentOS or any other RHEL-derived system, follow the first half of the guide; to install on Debian or Ubuntu, skip to the latter half.
Similar to RDP for Windows servers, Ubuntu desktop and TightVNCServer will allow you to connect to a remote desktop running on your Linux VPS. This tutorial will guide you through the setup of a basic desktop and VNC server.
VNC is a desktop sharing system that will allow you to connect to a Linux desktop from your home PC, for easy remote management of your VPS. This walkthrough will guide you through the installation of a VNC server on Debian.