Mechanos7 has created a multiplayer game called Spam! It is a simplistic round-based game where two players compete by clicking every tile they can until they are all taken. The player with the most tiles clicked is the winner. This is a fast paced game and each round should take no longer than a minute.
Ripper man5 has released a new Yahtzee! game. For now, it can only be played in single player, but this might change in the future. He's also planning on some unspecified further improvements down the road, as well as installing a high scores table on the hub page. Since this is a fresh release, be aware that there are likely some bugs that are still in need of squashing.
Solcolito_Butch has posted on the BYOND Casual forum about a game he is developing called Craze Maze. When its finished, this game will contain (not surprisingly) large mazes. But not just ordinary mazes, these mazes will include secret passages, hidden rooms, traps and some unspecified "special gifts" to discover. This game will support user-generated content, meaning you can create your own mazes and share them with other players. There will even be stories to play through, both in single player and multiplayer.