Well, here's what I can dredge up from just one source. I am sure there are better sources out there. This from "Failure is not an Option" by Gene Kranz:
Chris Kraft (probably senior flight director)
John Hodge (Bermuda flight director)
Gene Kranz (Assistant flight director?)
Al Shepard (CapCom)
Tec Roberts ("trajectory operator")
Others
John Llewellyn (some sort of controller)
Don Arabian (systems monitor)
I'm not quite seeing the titles you'd expect if you're used to the Apollo program...maybe the controllers hadn't yet clarified all those roles and titles by the time of Glenn's flight?!
Anyway, Wikipedia has further reading!
http://en.wikipedia.org/wiki/Project_Mercury
MT