A new official Pokemon tournament was announced recently. The format is much the same as the official VGCs (double battle format, nearly all moves and Pokemon allowed except high-powered legendaries), however, you play other people online over Wi-Fi.
Players must register for the competition beforehand and the deadline is the end of March 21st (Wednesday!) so register now if you want to take part! The competition itself runs from the 22nd to 26th March inclusive.
A Pokemon Global Link account is required. Find more information and register for the tourney here. Good luck!