Ok, let's get this archive of yours started.
I see Chris Young at meets all the time. He's generally a pretty cool guy, and a great coach.
I've run into Blaine Wilson a couple of times -- at one point he, I, and a couple other coaches went out for food and drinks after a performance (specifically, the Tour of Gymnastics Champions that goes around the US after every olympics), and he paid for everybody's meals. I hear he has a reputation for arrogance, but I've found him to be an awesome dude every time I've hung out with him.
At woodward over the years, I've hung out with Elise Ray, Dominique Moceanu, Morgan White, Tatiana Gutsu (who introduced me to a fascinatingly entertaining Russian tradition/superstition that has become a mainstay of coaches nights out at woodward).
At National Qualifiers last year, I hung out some with Charlie Tamayo and Joey Hagerty, and exchanged greetings with Ivan Ivankov and Vitaly Marinich.
Kristie Philips owns a gym in my state, so I see her at meets form time to time. They say that if you can't say anything nice, you shouldn't say anything at all. With that in mind
At woodward this past year, the Penn State men's team came in to train on the final day, so I spent an afternoon taking turns with Kevin Tan on rings, while Noam Shaham practiced the Shaham on high bar nearby. Also, Alexei Nemov was coaching.
Shawn Johnson was there that week, but wasn't particularly sociable.
As celebrities go, gymnasts are generally pretty accessible. Heck, there are probably a few others I've met that I don't even remember.