This is my "not-to-forget-steps-when-installing-ubuntu-server" document. It can be incomplete on its own. If you miss anything, take a look at the links I used.

Install a minimal server with F4 from the install screen.

Packages

Next you see a list of packages, but what for? These packages are used to run a system with the following services:

• webserver with support for a mysql backend which supports php. This configuration allows you to run joomla and gallery2 for example.
• Mailserver using postfix, dovecot, pyzor, dcc, razor, sasl, amavis, clamav, fetchmail, spamassassin. With this you have a complete mailsystem for a secure and spamfree mailbox. Also I use dovecot for quotas and it allows to have server based filters using the sieve plugin.
• Subversion to have a versioning system on your scripts (like CVS)

It also delivers some security:

• rootkit check tool by rootkit hunter
• denying access from unwanted system with the use of denyhosts

Security / tools / connectivity

denyhosts gnupg nmap openssh-server ssh traceroute screen subversion ntp ntpdate rkhunter whois policykit lynx

Webserver (including packages for gallery, like ffmpeg, imagemagick, gd)

apache2-mpm-itk phpmyadmin phpsysinfo mailgraph mysql-server imagemagick ffmpeg php5-gd php-pear libapache2-mod-php5 php5 php5-common php5-curl php5-gd php5-idn php-pear php5-imagick php5-imap php5-json php5-mcrypt php5-memcache php5-mhash php5-ming php5-mysql php5-ps php5-pspell php5-recode php5-snmp php5-sqlite php5-tidy php5-xmlrpc php5-xsl php5-cli php5-dev libapache2-mod-auth-mysql jhead

Mailserver

postfix postfix-mysql postgrey sasl2-bin libpam-mysql amavisd-new clamav fetchmail spamassassin dovecot-imapd dovecot-pop3d clamav-daemon zoo unzip bzip2 libnet-ph-perl libnet-snpp-perl libnet-telnet-perl nomarch lzop pax arj unrar cabextract fetchmailconf zip razor pyzor squirrelmail php-pear libhtml-parser-perl libdb-file-lock-perl libnet-dns-perl mailutils pflogsumm rar

DCC (part of the anti spam solution)

Unfortunately, DCC isn't yet part of the repository, so we do it by hand. You might want to check for a newer version.

 cd /tmp
 wget http://launchpadlibrarian.net/11564361/dcc-server_1.3.42-5_i386.deb
 wget http://launchpadlibrarian.net/11564359/dcc-common_1.3.42-5_i386.deb
 dpkg -i dcc-common_1.3.42-5_i386.deb
 dpkg -i dcc-server_1.3.42-5_i386.deb