FVWM is the famous fast-and-flexible free virtual window manager that's known for being incredibly configurable, and for being the ancestor of probably half the window managers in existence. I like it because it's lightweight and I can configure it exactly how I want it (which tends towards minimalist).
It's also know for being somewhat challenging to configure. The default config is fairly plain (or even non-existent). There is no GUI front-end for configuration. Building a config is something of a project. Thus it's common for people to share their configs, so I thought I'd share mine. I shun bling and flash that slow things down, but that's just personal preference — FVWM can be pretty, too.
My FVWM configuration
A (cropped) screenshot of my FVWM environment. As I said, minimalist.