In real life, or on any social media sites? I was just tweeted at by Smosh, and I've talked to Peter New, Andrea Libman, Dustykatt, Solrac, Mandopony, Tabitha St. Germain, AcousticBrony, Ibringdalulz, ibeabronyrapper, Tara Strong, and Michelle Creber, on Twitter.
I've yet to go to a convention, but I wish I could talk to all of them in person.