How many Ambercons are there, and where are they held?
Over the next year there are expected to be several conventions dedicated to Amber gaming: Ambercon, Ambercon UK and Ambercon NorthWest. The biggest of those thus far is Ambercon (sometimes known as Ambercon US). For more information on these conventions, check out http://www.ambercons.com.
You can also find Amber games at Gen Con, held every August in Indianapolis, Indiana; Blue Water Con, held each summer in Port Huron, Michigan; U•Con, held on a non-home football game weekend in late October or November in Ann Arbor, Michigan.