I've used Fluxbox and Blackbox basically since I was in diapers, but I recently decided that it's really way past time to try a tiling WM, and settled on xmonad after initially trying awesome. I like it a lot so far; it's lightweight, flexible, and very easy to configure, and I'm surprised how little I miss dragging windows around (although I still float some frequently used applications, Chrome and Audacious primary among them.)

I usually have a workspace for shell & filesystem stuff, one for emacs, one for documentation, one for running servers and monitors and other misc. utils for whatever I'm doing, and one floating one for web browser and music.