DirectFB is a thin library that provides developers with hardware graphics acceleration, input device handling and abstraction, an integrated windowing system with support for translucent windows and multiple display layers on top of the Linux framebuffer device. It is a complete hardware abstraction layer with software fallbacks for every graphics operation that is not supported by the underlying hardware.
YanC (Yet another nV Configurator) is a small tool which you can use to change the nVidia and ATI-specific settings (almost) as easily as with the Windows drivers. You can edit the settings for AGP support, the Cursor Shadow, the nVidia logo, Digital Vibrance Control, and, of course, TwinView for the nVidia drivers. For the ATI drivers, it offers support for the overlay settings, anti-aliasing, and dual monitor configuration.
Wacom ExpressKeys supports the fairly recent additions of ExpressKeys, Touch Strips, and a Scroll Wheel on certain Wacom tablets. Specifically the Cintiq 21UX Interactive Pen Display, the Intuos3, and the Graphire4 tablets are supported through the XInput and XTest extensions in X. Using "xsetwacom", it can also provide an automatic change of stylus pressure sensitivity (a.k.a. PressCurve) when going from one program window to the next. This feature is independent of the connected tablet model. A graphical configuration tool named "wacom-config" is under development.
GAMMApage is a program to adjust a monitor's gamma setting, either fully or by color. It is capable of setting gamma for most Linux distributions upon login, including those using ATI fglrx_xgamma. It works both for graphical logins or console logins. It only requires write access to the user's home directory, not to any system directories. It includes "preparation" tips with white and black point targets to make gamma corrections effective. This is the pumped-up, Python/GTK version of Monica.