Build your own Linux system with aid of the LinuxFromScratch project. This project provides a guide to build an base Linuxsystem(LFS) and beyond(BLFS) by compiling and installing from source. You can build it manually, but you don't have to. The LFS community provides tools to automate the build(ALFS)

Links:
LinuxFromScratch website.

Very usefull. I'm using it a long time now. Very usefull features like tabbed browsing, blocking of ads and scripts.

Links:
Mozilla website.

Mplayerplugins for Firefox, view any movie from the browser!

Links:
Projectsite mplayerplug-in.

Great desktop.

Links:
Website of KDE.

Great fun with this excellent musicplayer.

Links:
Website of Amarok.

A great addition: a sidebar for the KDE filemanager. Very userfriendly and usefull! You can modify it behaviour and add your own links. I can't show detailed images here, but you should try it and convince yourself!!

I found out that Kmetabar does not compile with the latest versions of KDE (3.5.5 in my case). I've found a patch for that which was not so easy: kmetabar-fix.patch

Links:
Kmetabar at kde-apps.org
Patch ot build it with latest versions of KDE.

Work on your own desktop anywhere. This is already possible with other techniques, but FreeNX provides near local speed application responsiveness over high latency, low bandwith links, for example the Internet.

Here shown is a Linux desktop, running a Gnome session on the server.

A guide to build a FreeNX server on a LFS system from sources you'll find here

Check also the website of the original commercial product NX: www.nomachine.com for more info, client to connect to a server. Here you also find information to start a testsession to public NX servers.

Links:
Website of No Machine.
Projectsite of FreeNX.
Guide to build FreeNX 1.5 from source.

Usefull officesuite.

Links:
Website of OpenOffice.

Serve your website with the excellent webserver, httpd.
This website is served to you with it.

Other usefull software of the Apache Software Foundation is Spamassassin

Links:
Website of Apache.

A very usefull tool to create dynamic websites is PHP.

Links:
Website of PHP.

Let your users share their documents with this OpenSource replacement of the well known Microsoft Primary Domain Controller. With this software you're able to let your Linux machine act as server or as workstation in an Microsoft Network Environment.

Links:
Website of Samba.

Build complete and safe firewalls with the software (iptables and ulog) of Netfilter.

Links:
Website of Netfilter.

Monitor your computers with this very good software. Excellent monitoring tool.

Links:
Website of Munin on Sourceforge.

POP3 and IMAP server which stores the messages in a SQL server..

Links:
Website of dbMail.