Currently procrastinating data cleaning/analysis... so I'll start...
I've been working in a social psych lab in a small college. It's the dept head's lab, which doesn't mean much at all, and we primarily do work on a longitudinal study that's been going since 2006. At a small school (with no graduate students in psych), roles often overlap and so I am the lab manager and the "older student" who mentors younger students when they arrive in the lab. It's a very rewarding experience, but since nobody truly understands the purpose of my job it can be frustrating! Two of "my" students have gone on to publish and many more to conferences... I am in the middle of publishing my first paper and I have been to a few conferences here and there. I actually do get paid, but I'm the only student that does get paid and it's not much. Gotta get that resume booster + I love it anyway! My PI treats me very well and I am sorry I graduate this Spring.
What grad schools (and my "competition") see: hasn't published (yet), a few conferences, thinks "mentoring experience" is lab experience.