nssjson is a (not so) simple, fast, complete, correct and extensible JSON encoder and decoder for Python 2.5+ and Python 3.3+. It is pure Python code with no dependencies, but includes an optional C extension for a serious speed boost.
nssjson is a fork of simplejson that fulfills my need of having a good performance JSON encoder/decoder able to handle also Python's datetime and UUID, even if with an admittedly non-standard and faulty heuristic that was not considered within the scope of the original product.
Practically, the difference is that, out of the box, you have:
>>> import datetime, uuid
>>> import nssjson
>>> now = datetime.datetime.now()
>>> uid = uuid.uuid1()
>>> nssjson.loads(
... nssjson.dumps([uid, now], iso_datetime=True, handle_uuid=True),
... iso_datetime=True, handle_uuid=True) == [uid, now]
True