The warning at http://docs.python.org/library/subprocess#frequently-used-arguments should IMO recommend using shlex.quote.  Even if it strongly advises against using shell=True, there are people who need or want to use it, so let’s give them a pointer to the quote function.

For older versions, I think we should talk about pipes.quote; even if it’s not documented in library/pipes, it is there, it is known and it is used, so I see no harm in mentioning it (with due mention that it’s only semi-official and that it becomes public in 3.3).