Network services

Security

• Iptables - (Netfilter)
• SSH - (OpenSSH)

DNS

• Bind - (Bind DNS)

HTTP

• Apache - (The Apache HTTP Server Project)
• Tomcat - (Apache Tomcat servlet container)
• Nginx - (HTTP and reverse proxy server)
• Lighttpd - (Lightweight open-source web server)
• Squid - (Squid home)
• Varnish - (Varnish Community | Varnish makes websites fly!)

• List of HTTP header fields - Wikipedia, the free encyclopedia

E-mail

• Exim - (Exim)

FTP

• Vsftpd - (Very Secure FTPD)

Utilities

• Visual Subnet Calculator
• Network test