I saw at over at the GBase that the people behind the fan-made UFO: Alien Invasion have officially opened their website. You might want to take a look at this one if UFO: Aftermath hasn't fully satisfied your X-COM lust. According to the crew their project is not meant to be a remake of or a successor to the X-COM games, but is "heavily inspired" by the Microprose classic. Like the original series, Alien Invasion is said to be turn-based strategy title. Of course, technology research is essential for your progress and success. And there's more to the game, which actually has the Quake 2 engine running beneath it:
You can play UFO: ALIEN INVASION with your friends via LAN or Internet. One player takes the role of the human special squad while the other is in control of the alien invaders. Co-op team play with multiple players on both sides is also supported for up to three teams on each side (6 players total).
They've put up some shiny screenshots in addition to that. The team is currently working on a demo of the game, which may or may not be available by the end of February. We'll definitely keep an eye on this one. Some of the North-American gamers among you are probably wondering what the whole "UFO" deal is about. Well, the first X-COM game was released as UFO: Enemy Unknown in most parts of Europe.