If you had the same tool that worked with a blog search API not only would I pay for it, but you could sell it to SEOs all day long. Just need to find a decent blog search API; I haven't had much luck.
That said, I've actually used mechanical turk to earn money in some of my low points (was living in my car working on a startup, out of cash, crazy/long story). I didn't make US minimum wage, but if I were living in Bangladesh, for example, it would have been OK money.
Say I'm a bowtie company that sells to designers; I could look for all the fashion blogs by searching "bowtie" or "necktie," etc. Just generic blog outreach, whether it's little blogs or mommy blogs, would be very useful. Not only do you get some traffic from those blogs, but you get the link juice of some really good links.
It works manually really, really well.