Ion is a tiling (no overlapping windows) window manager that also has
PWM-style tabbed frames which can contain multiple client windows. These
features help to keep windows organized and to switch quickly between them.
Ion was designed primarily as an efficient and unobtrusive window manager 
for users who prefer the keyboard. 

This is the latest stable release of Ion (3). A pwm3 binary is built
too, which starts Ion with floating workspaces as the default, thus replacing
the PWM window manager.

Please note that the author of Ion stopped all development and support for
this tool - even its web page has been taken offline.

A community effort started a forked project called "notion", which can be
found at http://notion.sourceforge.net/