Well, I run a video game forum, so we use Xbox Live and Playstation Network to help get potential users. Not sure if you consider that "offline" or not.
We also have members bring in friends, as well as school mates. We have users that work in gaming stores, so they'll tell customers about it, and hand out a few fliers if they won't get in trouble. Some schools even have video game clubs, which we try to target.