Although I administer most servers via SSH, I also use Webmin. Webmin is convenient for almost any simple administrative task, and is often better for some jobs. For instance, it is the easiest way I have found to browse Postfix email queues. Perhaps most importantly, it can save you from having to learn yet another daemon’s unique configuration language and syntax.
It can also be very handy if you have to fix something from your smartphone, where the command line isn’t always the best choice of tool. Enter: the Virtualmin Mobile/iPhone Theme.