… is a matter of taste, but this is (part of) my list:

# For general use:
aptitude install zsh less strace psutils rcs screen rsync sshfs ntpdate host exim-daemon-light uemacs
# For server maintenance
aptitude install munin-node munin-plugins-extra
# For development use
aptitude install dpkg-dev debhelper

At least for uemacs you need to access the /usr/local repositories. This /etc/apt/sources.list.d/usr-local.list will do:

deb-src http://debian.usr-local.de/debian sarge local non-free contrib
deb     http://debian.usr-local.de/debian sarge local non-free contrib
deb-src http://debian.usr-local.de/debian etch  local non-free contrib
deb     http://debian.usr-local.de/debian etch  local non-free contrib
deb-src http://debian.usr-local.de/debian lenny local non-free contrib
deb     http://debian.usr-local.de/debian lenny local non-free contrib
deb-src http://debian.usr-local.de/debian lucid local non-free contrib
deb     http://debian.usr-local.de/debian lucid local non-free contrib

deb-src http://debian.usr-local.de/debian gutsy         non-free
deb     http://debian.usr-local.de/debian gutsy   local non-free contrib
deb-src http://debian.usr-local.de/debian oneiric local non-free contrib
deb     http://debian.usr-local.de/debian oneiric local non-free contrib

To change the timezone of a running systems, issue

tzconfig

or

dpkg-reconfigure tzdata

depending on your version of Debian.