I have just stumbled upon this forum page http://moodle.org/mod/forum/discuss.php?d=7373 which references a 'hidden' Moodle page which can set all user timezones to a given value all at once. (I was just about to do this on the live database and was wishing there was another way...)
The page in question is http://yoursite/admin/timezone.php, and it's still in there (the forum post is ~5 years old), and my point is twofold:
1) how many other pages are there in Moodle, which are hidden, which do very useful things, and:
2) can they be made available to admins in a separate section of the admin menu?
Another example is the userpics page, which is useful and not too many peope are aware of.