Easy extend seems to be about creating DSLs in python. It allows parsing from an ebnf grammar and can extend the python grammar for the language. You can download EasyExtend.
It compiles these defined languages to the python parse tree, this is then compiled to python bytecode by python. It can run multiple different languages within one python run, by a concept called fibres.
I don't know if it's really apealing, since it seems pretty much tied to the python runtime. For instance, can somebody tell me if I can create new syntax, for instance for a anonymous function? It seems like that's possible, the hard thing is changing not just syntax but changing semantics.