The Apache HTTP Server is the most widely used web server in the world. The Apache server has a wide range range of modules and supports many programming languages including PHP, Perl and Python.

BIND is the most widely deployed DNS server in the world. Developed by the Internet Software Consortium, it provides and authoritative and recursive DNS server and meets the IETF DNS standards.

ClamAV is a powerful Open Source anti-virus engine and virus detection tool-kit for UNIX and Windows. ClamAV is ideal for embedding in spam and web filtering products.

Dovecot is an open source IMAP and POP3 server for Linux/UNIX-like systems, written primarily with security in mind. Dovecot is among the highest performing IMAP servers while still supporting the standard mbox and Maildir formats. Dovecot gives complete IMAP4rev1 and POP3 support. IPv6, SSL and TLS are also supported.

Exim is a highly configurable, Sendmail compatible SMTP server. It is well documented and features strong access controls, mail routers and the ability to integrate with external spam and AV filtering tools. It is the default MTA on Debian as well as being used by cPanel web hosting software.

Nginx is a flexible, high performance web server, reverse proxy, load balancer, mail proxy and HTTP cache which was originally developed to solve the problem of how to handle 10,000 concurrent connections

OpenLiteSpeed is a high-performance, event-driven Open Source web server with Apache compatible rewrite rules.

OpenVPN is an Open Source VPN server which provides encrypted point to point tunnelling, in either routed or bridged configurations between individual nodes, or between sites. It uses SSL/TLS keys and certificates to encrypt and authenticate users and supports firewall NAT traversal.

Postfix is a best of breed high performance, secure mail transfer agent (MTA) with an extremely comprehensive feature set, including virtual domains and mailboxes, mail routing and address rewriting.

Samba is a long established Open Source implementation of Windows SMB/CIFS file and printer sharing. A Samba server can integrate with a Windows domain, acting as either as a primary or backup Domain Controller and supports both Active Directory and NT style domains.