http://www.resistanceandliberation.com
This is a World War II mod, so it's free for anyone to download and play. It is a Source engine game, which means that "anyone to download and play" is limited owners of any Source game (CS:S, HL2, TF:2, and so on).
For anyone who has played Insurgency, this is similar to that, but in my opinion, much better. Most maps are relatively big and very well done. Voice chat is built in, but only people around you can hear you.
There really is plenty to talk about, but I rather keep this short. This is a great game, but doesn't have that many players. The number of servers are low, but I'm sure East Coast/Europe should have a good time with less lag then I would get being on the West.