Actually there are not many programs specifically written for wmaker -I mean that depedn on libraries supplied by wmaker. fsviewer is one. The wdm display manager is about the only program dependent on wmaker which ever had any popularity. There are many DockApps 'designed for wmaker', but which can be used with other window managers. A very few of them link directly with wmaker libs, others link to libdockapp(which is not part of mwaker, some link to old gtk+ libs and many use only Xlibs or Xlib with some other toolkit.
DockApps are very nice -but only a few of them are really useful at a normal (48x48) icon size -network monitors and such.
I have used wmaker nearly exclusively for over 10 years -most of that time with about the same setup. I run wmaker with a nice panel at the bottom (called Taskbar) and run the ROX-Filer(old gtk+1 version) to manage desktop icons. I actually turn the wmaker Dock and Clip off, plus all miniwindows.
For the bulk of *applications*, you'll inevitably wind up running apps which use some gtk, qt, or kde libs. The lighest of course would be gtk+. None of the 'small, light toolkits' like fltk will help you since there are only a few apps available for them.
There are WM's which use less RAM than wmaker, but I found it a very nice step up from fluxbox, etc. icewm is another light one I like, but since a long time it needs gtk+2 -which I avoid as much as possible. I have gathered a bunch of gtk+1 programs for basic things like creating archives, managing files, etc and only gtk+2 with seamonkey and a few others. Anything critical which needs to be kept up-to-date -like browser or other network tools use gtk+2. But all the stuff which is always running underneath is either gtk+1 or Xlibs.
Here's a humorous look at an atypical desktop:
If you notice in the lower right cormer there are two DockApps running -a CD player and a network monitor. At the bottom is the 'taskbar' panel -sorry the clock is not showing... All the rest of the desktop icons are created and managed by the ROX-Filer -some of them are ROX AppDirs and others are simply 'shortcuts' to things.
I used to use the wmaker Dock and sometimes the Clip in a normal wmaker way, but a single app running from the Dock means there are three icons showing for the program! Plus, any apps placed in the Dock will always be running -which leads to longer startup times for wmaker.