PyPy aims to be a fast JIT-compiled alternative of the Python language. PyPy tries to be faster than Python and utilize less memory while being highly compatible with existing Python code.
PyPy 2.0 changes include supporting stackless along with greenlets and that PyPy now has cffi 0.6 as a built-in module for calling C from Python. Other changes include callbacks from C now being JIT'ed, speed improvements, JIT improvements, stability fixes, and other improvements.
More details on the PyPy 2.0 release can be found out from the project blog.