Fluxbox is another window manager derived from Blackbox, with a different philosophy. While Blackbox is determined to be bare-bones on the features, Fluxbox cheerfully includes as many features as it can get away with. The result is a very handy, very unique environment; a perfect balance of the speed and stability of Blackbox and the cool look of almost-Enlightenment.
Fluxbox features include transparent elements, menus, and window decorations, customizable keyboard, window tabs, mouse-wheel desktop switching, and more menu-based tweaks for the environment such as window-focusing. It's theme engine is both backwards-compatible with Blackbox themes, and capable of using pixmaps and fancy fonts. It still keeps Blackbox's policy of having all the configurations be simple text files, so it's a hacker's paradise again.
Fluxbox has risen to be the most popular window manager, and nearly every major FOSS distro includes it. It sacrifices almost nothing in the speed department - the difference between Fluxbox and Blackbox is a mere fraction of a second.
Here again, it's a mixed bag whether it's right for a newbie. It is well documented, whether by the included manpages or by the complete HTML-manual at the home site. Like Blackbox, as long as a simple text file doesn't intimidate you, Fluxbox will prove no more difficult. Fluxbox can still be scripted and molded easily, and in fact has spawned another thriving fan-base who make custom programs to supplement the environment.
Of all window managers, Fluxbox most accurately hits the sweet spot between performance and looks. While prettier window managers will satisfy the show-offs, and faster window managers (of which there are very few, and by only fractions of seconds) will suit those who insist on top performance, Fluxbox has the most to offer for the widest audience. It's styles and extended ways to customize give it a look that puts it next to enlightenment, while still having the simplicity of Blackbox.
I would recommend Fluxbox for the web designer or the graphics artist. It's a cool-looking desktop that won't get in your way.