spectrwm is a minimalistic tiling window manager that tries to stay out of the way so that valuable screen real estate can be used for much more important stuff. It has sane defaults and does not require one to learn a language to do any configuration. It was written by hackers for hackers and it strives to be small, compact, and fast.
Tiling provides a simple window tiling system for Linux. It's for those who cannot (or don't want to) use a tiling window manager like awesome or Xmonad. There is no menu or GUI in tiling. You just (optionally) focus a window, press a keyboard shortcut, and that's it -- all windows in the current virtual desktop are tiled.
Bluetile is a tiling window manager designed to integrate with the GNOME desktop environment. It provides both a traditional, stacking layout mode as well as tiling layouts where windows are arranged to use the entire screen without overlapping. Bluetile tries to make the tiling paradigm easily accessible to users coming from traditional window managers by drawing on known conventions and providing both mouse and keyboard access for all features.
Notion is a tiling tabbed window manager for X. This means the screen can be freely divided into tiles that contain the client windows. Multiple client windows can occupy the same tile; in that case they will be tabbed, much like browser tabs. This way, windows will not overlap and it becomes easier to manage your screen real estate. Its functionality can be configured and even extended with Lua scripts. Various scripts are available, such as for NetWM features and multihead support.
subtle is a grid-based manual tiling window manager with a strong focus on easy but customizable look and feel. In comparison to other tiling window managers, subtle has no automatic tiling of the screen size in any way. Instead, windows are arranged according to positions inside of a grid. These positions are called gravities.