If you’re a fan of Openbox, you should take a look at urukrama‘s excellent guide to setting up an Openbox system. He’s collected a lot of the best information available on the excellent little window manager, updated it and reorganized it for easy digestion. I’ve already learned a thing or two from it.
Even if you’re not a fan, you should take a look. And if you’ve ever considered using Openbox you should definitely take a look, since it might be what convinces you to drop Gnome.