I was lucky to happen upon a number of wonderful mentors before and during graduate school, many of whom I still count as mentors now. These were people who encouraged me to push myself further than I thought I might go, but also reflect on what I really wanted to do and what made me happy. Encouraging this practice of working hard for things you really want and the processes of figuring out what you want and how to work hard to get it, is a big part of mentoring in my view.
Abigail adds: I have some experience working at the U.S. Census Bureau. There are a lot of really smart, great PhD's working in the federal government.