Something I learned on HN a long, long,long time ago was that if you wanted really cheap, unfiltered traffic, you could buy quite a bit of it using Mechanical Turk. As the commenter said "It's pretty amazing what will happen if you throw up a few nickels". I've only used it once, but it worked.

But with only $200 you want to make sure every dollar -- every penny -- counts towards getting action. So I would use it on the most targetted ads I could get. For most fly-by-night web apps that only have a $200 ad budget, adwords would be the best way to do this.