Which files in /var to back up?

[Krzys Majewski]

With the advent of apt-get and cable modems, it appears I no longer
have to back  up every file on my machine.  In particular, things like
debian packages can be easily retrieved after a crash, provided
that the appropriate status files exist. Presumably these are files in
/var  like /var/lib/dpkg/status or  maybe /var/cache/apt/*  ... anyone
know exactly which  files I should be backing up? I  could back up all
of /var but that seems a bit excessive, no? -chris