Generic programming project?

So I was wondering if you guys have a generic programming project, so that when you're learning a new language, you port this project into the new language you're learning to get practice with that language. The ideal project encompasses virtually 'every' facet of programming. (i.e. OOP, some datastructures, some algos, etc)

I usually design a dynamic user interface, preferably one that has elements definable by XML.

Take a look at the user interface in World of Warcraft for example, it's an excellent example of how dynamic such a system should be, and because of how well designed it is, it is very easy to modify/write addons for.

A good UI would encompass many OOP elements, and it was through making my own UI system with a component-based design structure that I really understood how to do OOP coorectly.