I've blogged a few times about how much I like PayPerPost. Forgive me if I repeat myself. ;)
I signed up with PayPerPost in August 2006. Because my blog didn't meet all of the criteria I didn't actually start takings opps (paid opportunities) until February of 2007. Since that time I've really only made a small effort. I keep meaning to sit down and carve out some time to make this into a real part time job.
In the meantime, I've made over $130 just doing this sporadically. It doesn't sound like much, but I can't tell you how nice it is to get that extra $5 or $10 every week or two. I don't keep real close track of when my payments are due, so it always comes as a nice surprise.
Another benefit of working with PayPerPost is that I find out about cool sites and services that I might not otherwise run across. Sites where you can win prizes, price health insurance, even learn where to list free classified ads.
I've already decided to take a portion of what I earn from PayPerPost & reinvest it into blog marketing. The rest of the money is going towards my running gear fund.