I'm not sure if I've posted this before, but if you Debian users drop this in root's crontab, you'll save a whole lot of download time:
# cache latest packages at 5am 1 5 * * * apt-get -q update && apt-get -qfmuy --download-only dist-upgrade
That'll cache the latest packages every morning. This isn't my idea, I stole it from Tom (giblet), and I have no idea who he stole it from.