I tend to disagree with Ezio about a FAQ for general questions.  A pointer to appropriate alternatives for off-topic posts in the Mailman listinfo descriptions of the various list (which can be copied into the devguide, or linked from there) will be sufficient for people who actually read such things before posting.

OTOH, once there already is a misdirected post, I feel it's appropriate to say "This post is off-topic here because this list is for development of Python itself, not developing applications with Python.  Posts like yours are ignored  by almost all participants.  You will get help (possibly better than you could get on this list) on Python-X@python.org."  Adding a pointer to a FAQ which just repeats the same thing is browbeating IMO.  It's not like we don't have several people who have macros to say the above (and more politely than I did) who typically respond within hours to off-topic posts.  What more could a FAQ say?  Of course this needs to be on-list so that the poster (who usually is a little feckless rather than deliberately abusive) doesn't get spammed, and so that the multiple volunteers who handle these posts don't duplicate each other.

I personally would like to see a guideline to participants that if they want to offer advice on the question itself to people, that they do so off-list.  Whatever one's opinion on the utility of offering advice in response to an off-topic post, such advice is as off-topic as the question that elicits it.