Hmm... Mike Smith coded a script for the Ultimate Sims List that will look up the front page of a site and read its header. That might be the crawler you're thinking of.
I'd never thought of the Ultimate Sims List as a revenue producing site; other than begging for donations to help pay the costs. (Donations to date have been near zero so I'm just paying for all this mischief out of my own wallet. It's not too expensive; I think it would be a little more than $100 a month if I added it all up.) I don't know if the big sites would be willing to pay for top ranking or not, but I suspect just asking them to would generate a lot of negative publicity and feedback that I don't want to deal with.
Those are some great ideas for how to make the Ultimate Sims List more useful and fun in any case. I'm not even working on it at the moment because I'm sort of distracted by Real Life; that is, looking for a job.