Luckily, I was writing in personal finance for a few years before I joined Mint so I knew most of them. Some of them included Ramit at http://iwillteachyoutoberich.com, Cap from http://stopbuyingcrap.com and Jim at http://bargaineering.com to name a few.
We just went and interviewed the guys above or asked thme for guest posts. You have to think how to serve their interests (traffic / exposure / relationships with a potentially cool company).
Yea, the Mint blog.