Sawfish is an extensible window manager using a Lisp-based scripting
language. Its policy is very minimal compared to most window managers.
Its aim is simply to manage windows in the most flexible and attractive
manner possible. All high-level WM functions are implemented in Lisp
for future extensibility or redefinition.

These are some of the features that set Sawfish apart from other window
managers:

* Powerful key-binding: Virtually every functionality provided by Sawfish
  can be bound to keys (or mouse buttons).
* Event hooking: For many events (moving windows etc.) you can customize
  the way Sawfish will respond.
* Window matching: When windows are created you can match them to a set
  of rules and automatically perform actions on them.
* Flexible theming: Sawfish allows for very different themes to be created
  and a variety of third-party themes is readily available

WWW: http://sawfish.tuxfamily.org/