Notion is a tiling, tabbed window manager for the X window system:

* Tiling: you divide the screen into non-overlapping 'tiles'. Every window
occupies one tile, and is maximized to it
* Tabbing: a tile may contain multiple windows - they will be 'tabbed'
* Static: most tiled window managers are 'dynamic', meaning they automatically
resize and move around tiles as windows appear and disappear. Notion, by
contrast, does not automatically change the tiling. You're in control.

Features include:
* Workspaces: each workspace has its own tiling
* Multihead: the mod_xinerama plugin provides very nice dual-monitor support
* RandR: mod_xrandr picks up changes in the xrandr configuration without the
need for restarting Notion (read this, though)
* Extensibility: Notion can be extended with lua scripts. Browse through the
scripts collection