Just started trying this game out. It's a play by e-mail phased real-time squad based strategy game from Nick and Julian Gollop, the creators of the first 2 X-Com games. By phased real time I mean that you and your opponent submit their orders seperately, then the results are computed simultaneously.
Just started my first match and it seems pretty cool so far. It does cost $15 for 6 months if you want to play in the league and be ranked, and if you want to submit your own challanges. However, if you want to play for free, all you need to do is ask for a challange on the message board at the website.
There are 3 different races you can play. Marines, AI (robots), and some wierd alien race (forgot the name but they seem similar to the Zerg in starcraft)
The site is http://www.lasersquadnemesis.com