Parlay is the largest online bingo software provider period. They were the first online and have kept a dominant position by constantly improving and diversifying their product offerings. Sites utilizing the software include The Bingo Associates Network and Yahoo Bingo.
The parlay sites have refined user interfaces designed to be intuitive for inexperienced users and efficient for savvy online players. Since they have been a player in the industry for so long, they are relatively diverse from Flash based Bingo Ballroom and software based Bingo Hall (also offers Flash, Java or software) to the much beloved Yahoo free bingo games.