Exim - Open Source message transfer agent

Exim is a message transfer agent (MTA) developed for use on Unix systems connected to the Internet. It is freely available under the terms of the GNU General Public Licence. In style it is similar to Smail 3, but its facilities are more general. There is a great deal of flexibility in the way mail can be routed, and there are extensive facilities for checking incoming mail. Exim can be installed in place of Sendmail, although the configuration of Exim is quite different.

Banshee - Open Source Music Player

Play your music and videos. Keep up with your podcasts and Internet radio. Discover new music and podcasts. Keep your portable device loaded with good stuff.
Banshee is a cross-platform open-source media player, called Sonance until 2005. This open source music player uses the GStreamer multimedia platform for encoding and decoding various media formats, including Ogg Vorbis, MP3 and FLAC.

SQUID – A Unix based Proxy Server

Squid is a caching UNIX based proxy server that caches internet content closer to a requestor than its original point of origin. This open source proxy server supports caching of many different kinds of web objects, including those accessed through HTTP and FTP.

Squid had many advantages which include

• Speeding up a web server by caching repeated requests
• Caching web, DNS and other computer network lookups for a group of people sharing network resources
• Aiding security by filtering traffic

HoTT Proxy – Open Source HTTP Proxy

HoTT Proxy is the open source HTTP proxy targeted specifically toward serving the needs of wireless Internet devices (cell phones, PDAs, etc.). It Provides HTTP (WAP 2) proxy capability (as opposed to WAP 1.x) and also proxy cookie support It allows you to restrict access by requiring a UserID and password.