Apt-listchanges

apt-listchanges shows the changelogs (and NEWS.Debian entries) of Debian packages. It can be called manually from the command line, but normally it is called automatically by apt when installing/upgrading (it installs itself in /etc/apt/apt.conf.d), so the user can review the changes and see what's new and to decide if he/she really wants to upgrade.

It has several frontends to show the changelogs e.g. pager (more,less,etc), pager in xterm, web browser, email. This can be configured with dpkg-reconfigure apt-listchanges