where can i get 3-way backlinks?

a while ago, there was a website that facilitated the making of 3-way backlinks, but i dont remember what it was.

I have 2 sites, site A and site B. I would like to find partners that will put a link to site A on their site. in exchange, I will put their link on site B.

are there any websites where i can find partners to do this with?

find SEO forums and services like linkspun