Gnome Display Manager
Gnome Display Manager is a re-implementation of the well known xdm program. gdm consists of three separate parts: A small daemon, a graphical login program (gdmgreeter) and a host chooser.
Light Display Manager
Light Display Manager (LightDM) is a fully themeable, cross-desktop, standars compliant display manager.
SDDM is a modern display manager for X11 aiming to be fast, simple and beautiful. It uses modern technologies like QtQuick, which in turn gives the designer the ability to create smooth, animated user interfaces.
wdm combines the functions of a graphical display manager identifying and authenticating a user on a system with some of the functions of a session manager in selecting and starting a window manager. Optionally, wdm can shutdown (reboot or halt) the system.
XDM-Choose is a highly configurable replacement chooser for XDM, which allows the user to type in a hostname and query/connect to it.