One of the best articles on initially configuring an Ubuntu system is from Slicehost, it goes into
Changing your port
Updating you firewall
Some general command line tools:
% lsb_release -a (What version of Ubuntu are you running?)
% cat /etc/lsb-release (What version of Ubuntu are you running? )
Some tools I find useful when doing upgrades:
Here is a great article upgrading from 7.10 to 8.04 (Gutsy to Hardy).