PEP 342 describes simple coroutines for Python. Coroutines are essentially mini-threads with manual control - you can freeze code in the middle and restart it with a new defined value. Thus, coroutines provide the first step towards primitive continuations - the only thing missing would be the ability to copy a coroutine.
Philip J. Eby writes about the implementation of this PEP - which, by the way, is based on Python's generators and iterators.
Come on, folks, finally ensure that generators are copyable and it's done.