IceWM is a lightweight stacking window manager for X11. It is small, fast and easy for new users. It has a task bar with applets and a pager for virtual desktops. It is very configurable and themable. Many beautiful themes exist. It supports backgrounds and sounds. It's documentation has recently been reworked and updated.
Ranked in these QuestionsQuestion Ranking
Pro Very good performance
IceWM is small and extremely fast.
Pro Excellent documentation
Since 1.4.2 and later docs are extensive and up-to-date.
Pro Beautiful themes available
There are plenty of pre-built beautiful themes available.
Pro Very configurable
A great many options to configure it. Though this is not required.
Pro Keyboard operatable
Many keyboard shortcuts exist. More can be added.
Pro Multi-monitor fully supported
Supports both XRandR and Xinerama for multiple monitors.
Pro Very Lightweight, configurable, can use as little as 4 mb of memory for window manager and tray with 4 desktops and menus with icons
Con Very bad for design
Not recommended if you like beautiful windows.