Reading through the forum it's apparent that many web admins settle on a common setup for their domain hosting: VPS + Virtualmin + Google Apps. Some also use external DNS service.
With this setup, some of the traditional functions of a web server become redundant and can be disabled, in order to free precious RAM for other services to perform better.
There is a guide for Virtualmin on low memory systems (http://www.virtualmin.com/documentation/system/low-memory), but there are still some questions and occasional issues that are not covered there.
So I'll start a thread for each of the main functions of a web server, and hopefully all the and knowledge and wisdom of Virtualmin gurus will be collected for everyone's reference.