I honestly have my doubts about whether this is a good idea or not. I know it can sound tempting, but If you're talking about protests and flyers and the like, I think you are only playing into the Society's hands. Witnesses and "worldly" people alike tend to see such efforts as the kind of things only weirdos do. I'm not saying this makes you a weirdo, only that most people shrug at stuff like that and forget it a day or two later. Even worse, it gives the WT someone to point and laugh at. I really don't think it makes much of a difference in the long run. Most people just don't care enough to listen unless they are already anti-WT. Which helps no one. Besides, if you are busy fighting the WTS, then it is--in a sense--still dominating your life. Moving on is far better. Like others have said, living well is the best revenge. I think people who join the Society often do so because they are looking for something. Most of the time, they'll give it a try so long as the Witnesses they meet seem friendly enough. Warnings rarely impress people who are searching like that.
If you are just talking about informing people, then there are other problems. You have to seem trustworthy and reasonable. Yet the bigger your efforts, the less believable you will seem. "Who would spend so much time and money on a project like this if they weren't passionately anti-WT?" they'll ask. "How can I trust this person's opinion? Who should I believe--the pro-Witness zealot at my door, or the anti-Witness zealots? Maybe I should go start going to the meetings and find out for myself..."
The Witnesses can seem very reasonable to people who don't know any better. (At first) It's hard to denounce a group like that without coming off as a little crazy or prejudiced yourself, even if your efforts are fairly mild. You may even help the Society make converts if you aren't very careful. More often than not, groups like the WTS get you coming and going. I doubt many people take the anti-WT sites you see too seriously unless they are already anti-WT. But that helps no one.
How can you put forth any major effort without looking like an anti-Witness zealot with an axe to grind? I think that's the very first question you have to ask before you consider going forward. Why should people listen at all? Why should they believe your story and not the WT's? You have to be subtle and make your message appealing. A big organization will probably undermine those efforts. But that's just my POV.
IsaacJ