Aside from twm which comes with X and mwm which comes with Motif, the system currently has:

fluxbox-0.9.9
icewm-1.2.14pre14
pekwm-0.1.3
xfce4-4.0.5

The first GUI I ever used was KDE and it nearly made me ditch Linux. Then I think my first successful compile ever was ratpoison and I had a lot of fun playing with it. Blackbox became the first wm I used for an extended period of time, followed by fluxbox for even longer. Then I gave ice a second try and either flux's devel series lost me or ice stole me away. But I still keep an eye on flux and play with others.

XFce4. Have yet to find a DE/WM that does a better job at being both fast and easy to use.

Standard (not Dropline) GNOME 2.6

Fluxbox 0.9.9 and aterm

FVWM2 with basic stuff
gkrellm, filerunner,gxine,gmplayer,firefox,sylpheed,midnight commander, xterm, gvim, nedit, acroread, openoffice, lyx, gftp, gaim, amsn, gimp, xmms, ghostview, acroread, eclipse, oxygenxml editor, imagemagick, nmapfe,xdvi.

I used to run fluxbox/rox but i find fvwm more flexible as it can emulate most of wm.

Catacomb 5.58

Definitely XFce 4.05, the best of the DEs (IMHO).

Utilize a diversity of KDE, Gnome, Gtk, CLI oriented apps...

Enlightenment Check my user screenshot for a look or visit here

Blackbox.

Fluxbox and sometimes Ion

KDE

I use KDE but I mostly just open up a bunch of terminal windows and have at it KDE is a nice polished desktop enviro and since i have 1024mb ram its not much of a problem..ha

Fluxbox-0.9.9 all the way.

blackbox 0.65.0

fluxbox 0.1.14 patched