I consider Three Worlds Collide a very strong candidate for the best piece of writing on LW (and, for that matter, miles ahead of HP:MoR, which I still enjoy immensely).

As a bonus, it also seems one of the easiest to market through a two-line AdSense. The most effective option might be going for the "WTF?!" angle; say, Aliens eat babies and want to sex us. A tale about rationality. I think curiosity would not be an uncommon reaction in the face of that.