Is there a way of updating spamassassin rules?

["Robert S" <robert.spam.me.senseless@gmail.com>]

I run sarge at work and gentoo at home.  On my gentoo box there is an
"sa-update" script which updates spamassassin rules, without requiring
that spamassassin is completely updated.  Is there an equivalent
script that will work with sarge?

I realise that there is Rules Du Jour, but I'd like to use something
that's vaguely "official" on a work box.