XGngeo is a full-featured GTK2 frontend, written in Python, that provides to end users a practical and user-friendly interface over GnGeo which is a fast and powerful command line Neo Geo emulator for the Unix platforms.
AFX is an X11-based, extensible, graphical, and highly configurable frontend primarily for use on tv-connected systems. The original design goal is a joystick-controlled frontend for an entertainment (games, emulators, audio, and video) box.
A cross-platform emulators frontend with ROMs database support.
Start-Game T00L is a cross-platform emulator frontend and ROM manager coded in Python using a Pyglet-based interface.
It's still on a very early stage of development, and most of the features are not implemented yet.
The goal is to make a fully functional frontend which works straight out of the box, without the need to configure every single emulator (like you need to do in every other frontend today).