Webmin is an excellent web-based interface to your *nix based machines. There are no webmin packages in the latest release "Dapper". This is how to install webmin to a Dapper server install...
(Update 2/24/2008: I do this on versions of Ubuntu up to the latest beta release also or on Debain (etch, lenny so far))

1. Install SSH

apt-get install ssh

2. Enable the universe and multiverse repositories in the /etc/apt/sources.list (https://wiki.ubuntu.com/AddingRepositoriesCliHowto)

3. To make this easier use a ssh client like Putty or a Term on another machine that has a GUI and copy/paste these commands or you can just re-type them...

Below is the source I just happened to use. If it is not working go to:

http://prdownloads.sourceforge.net/webadmin/webmin-1.470.tar.gz and find a working mirror.

First become root...
sudo su

Now, lets put the webmin software somwhere that it will not get in the way.

cd /opt
mkdir webmin
cd webmin

wget http://easynews.dl.sourceforge.net/sourceforge/webadmin/webmin-1.470.tar.gz
gzip -cd webmin-1.470.tar.gz | tar xvf -
apt-get install libauthen-pam-perl libnet-ssleay-perl libpam-runtime openssl perl perl-modules
cd webmin*
./setup.sh

Basically just hit enter and choose SSL and the auto start the service at boot
Web server port (default 10000): (Feel Free to change this)
Login name (default admin):
Login password: AReallyGoodONE
Password again: AReallyGoodONE
Use SSL (y/n): y
Start Webmin at boot time (y/n): y

Now you can login with the user/password that you set at the https://IpAddressOfYourMachine:10000