I have seen many projects using
simplejson, added to the stdlib. But since
json was added in 2.6,
simplejson has the advantage of working on more Python versions (2.4+).
simplejson is also updated more frequently than Python, so if you need (or want) the latest version, it's best to use
simplejson itself, if possible.
A good practice, in my opinion, is to use one or the other as a fallback.
try: import simplejson as json except ImportError: import json