Just now I found a new site sponsoredposts which is a site similar to payperpost. This is a brand new site and is yet to be developed. Right now they are they are yet to launch their website. I will just write what they informed on their site

"Enter your email address to receive notification and a chance to participate in our beta, when Sponsored Posts launches."

So, right now you need to provide your email and then when their site is launched they will inform to your email.