Hop is a new higher-order language designed for programming interactive web applications such as web agendas, web galleries, music players, etc. It exposes a programming model based on two computation levels. The first one is in charge of executing the logic of an application while the second one is in charge of executing the graphical user interface. Hop separates the logic and the graphical user interface but it packages them together and it supports strong collaborations between the two engines. The two execution flows communicate through function calls and event loops. Both ends can initiate communications.
It seems to be implemented in Bigloo Scheme and the demo's look very nice.