Apache HTTP Server
The Apache HTTP Server, which is often named as "Apache", is the most commonly used webserver in the WWW. It is designed modularly and therefor can be adapted to exactly the needs of the webmaster. In addition to this, it is available for nearly every operating system. Even when it does not host the application itself, the HTTP Server in combination with the modules mod_rewrite and mod_proxy could be used as a webpage proxy. With XAMPP there is a easy to use bundle of most common open source software for the web (HTTP Server, Database, FTP Server, PHP and Mail Server).
Tomcat
Apache Tomcat is a widespread JEE container and web server. It is part of the apache project (http://www.apache.org/) and is available open source under the apache license. As an JEE container it serves to provide Java based web applications (Java Enterprise Edition). Furthermore it offers fundamental functions for deploying applications, logging and user administration.
E-Mail was one of the first applications, which was used in the World Wide Web. Today it is still an important part in the daily business correspondence. An E-Mail server consist generally of different components which can fulfilled by etablished and spread Open Source technology. Components of a mailserver are a mail transfer agent (mostly Postfix), a mail delievery agent (e.g. Courier or Dovecot), Anti SPAM (e.g. Spamassassin), Antivirus (e.g. ClamAV) and webmail. Unfortunately it is not very easy to set up a secure mailserver, because all components need to be configured correctly to not being a mail relay abused by Spammers.
Debian
Debian is a Linux distribution which sets a high value on stability and security. This is perhaps the main reason why it is often called "the" operating system for servers. One the impressive features is the Debian paket system, which makes it easy to keep all the installed software up-to-date. In times of automatic attacs by distributed bot nets this is an important factor for server, that need to have a maximum uptime.
With Ubuntu there is a Linux derivative often used for client PCs, that is based on Debian and its paket system. Here an first hand example: The currently watched page runs on an Debian server that had its last reboot after more than a year uptime because of a defect in the network card hardware.
Piwik
Piwik is the follow-up project of the former phpMyVisits. It is a PHP based software to collect web statistics. The project gets more and more popular especially since the discussion about data privacy and the massive collection of data e.g. by Google.
With a few free space, an up-to-date PHP version and a database it is possible to collect data about your visitors and have descriptive reporting functionalities. The data stays on your server and is not transferred to other countries that often have less restrictive data privacy policies.
The development of the software goes fast and is already now usable for a productive environment. Generally spoken, Piwik is a good option to free offers like Google Analytics or other providers with cost.
Nagios
Nagios is the quasi-standard monitoring tool. The software allows the monitoring of complex IT infrastructures and can be roughly divided in two components: The first component, the so called Nagios plugins, provide a collection of modules to monitor various IT components. The second component is a web interface that allows the query of the data collected by the Nagios plugins. That means, Nagios can only be configurated by manipulation of files. Hence, it it mostly set up together with additionaly programs like Centreon that ease the creating and editing of these configuration files, for example via a web interface.
The Nagios modules can perform the monitoring active, e.g. via SSH, or passive, e.g. via SNMP traps. The modules return the determined state of the monitored component to the calling Nagios daemon. This daemon distributes notifications to the users depending on the configured alerting logic and reporting channels.
Zabbix
Zabbix is a server monitoring software comparable to Nagios. Nagios is on the one hand much more widespread than Zabbix, but on the other hand its support of reporting is only limited.
In a Zabbix setup various terminals (server, router, switches) triggered by certain events are informing the zabbix server about their state. This server consolidates the data and reacts at certain definable threshold values. These can be for example a lack of accessibility, exceeding a certain size of a pagefile, a defined network traffic or the cpu utilization.
The data is recorded and available over free periods as current values, but also as illustrative diagrams.