Dylan is an advanced, object-oriented, dynamic language which supports rapid program development. When needed, programs can be optimized for more efficient execution by supplying more type information to the compiler. Nearly all entities in Dylan (including functions, classes, and basic data types such as integers) are first class objects. Additionally Dylan supports multiple inheritance, polymorphism, multiple dispatch, keyword arguments, object introspection, macros, and many other advanced features... --Peter Hinely
For an overview of the available implementations of Dylan, see here.
None at the moment. Some will be coming soon!