Manfrotto Changeover - It Suits The Swiss
One notable one is the Manrotto rectangular PL200 plate - most bigger Manfrotto consumer tripods use this as the connection and it is a very good one. Another form is the Arca-Swiss plate used by that company, 3LT, Cullmann, and any number of other copyists. Unfortunately the Manfrotto rarely goes to Arca-Swiss.
Until now. This black casting with the bubble levels and large locking knob is the Manfrotto MSQ6 - it goes onto a Manfrotto ball head in place of the standard PL200 mount and allows you to use all the Arca-Swiss mounts. There is a safety pin to prevent untoward movement of the plate and you can twist it tight onto the receiver. It will hold immense weights.