XT-90 connectors are one of the highest rated connectors in use today.  These connectors are found on many of the higher-capactity, higher-voltage batteries sold today, and are required to handle the current used by many of the larger brushless motors.  Sold in Packs of 3 sets.
 
NOTE: The polarity is marked on these connectors on the back/side of each half, a very tiny + and - sign that is molded into the nylon body of the connector itself. Tin the ends of the connectors first, then insert your wires and add solder until the cavity is filled.