Dwm is a project mainly written in C, it's free.
My patched dwm
My patched dwm old version.
There's a newer, but I like this one. It's patched with
Some keybindings added (such as enabling screen lock).
Give it a try.
Pay special attention to config.h
There is no lighter window manager than this one :)
* NOTICE *****
This project is not mine. This is just my compile.
You can learn more about dwm in
http://dwm.suckless.org/