The part in the contribution documentation on "Submitting and maintaining translations" points to the Internationalization documentation, which in the section "A note to translators" just points back to the contribution documentation.
I was given some useful advice (http://groups.google.com/group/Django-I18N/browse_thread/thread/5d088c747d711104) that could be nice in the documentation, for what to do with an updated .po file:
"""Please make a diff [of the .po file] against the current subversion trunk version and attach the patch to a ticket in Trac [on the translation component maybe?].
Make sure that "bin/compile-messages.py -l fr" runs without producing any warnings before uploading the patch, since it cannot be committed with any syntactical errors."""
