Alfresco is the leading open source alternative for enterprise content management (ECM). It couples the innovation of open source with the stability of a true enterprise-class platform. The open source model allows Alfresco to use open source technologies and contributions from the open source community to get higher quality software produced more quickly at much lower cost.
Alfresco is led by John Newton, founder of Documentum, and John Powell, former COO of Business Objects, and is backed by Accel Partners, Mayfield Fund and SAP Ventures.

BackupPC is a high-performance, enterprise-grade system for backing up Linux and WinXX PCs and laptops to a server’s disk. It is highly configurable and easy to install and maintain. The program is written in Perl and extracts backup data via SMB using Samba, tar over ssh/rsh/nfs, or rsync. It is robust, reliable, well documented and freely available as Open Source on SourceForge.
Key Features

Optional compression support further reducing disk storage. Since only new files (not already pooled) need to be compressed, there is only a …

WPKG is an automated software deployment, upgrade and removal program for Windows.

ClamWin is a Free Antivirus program for Microsoft Windows 98/Me/2000/XP/2003 and Vista.
ClamWin Free Antivirus comes with an easy installer and open source code. You may download and use it absolutely free of charge.

WinDirStat is a disk usage statistics viewer and cleanup tool for Microsoft Windows (all current variants). WinDirStat reads the whole directory tree once and then presents it in three useful views: the directory list, which resembles the tree view of the Windows Explorer but is sorted by file/subtree size; the treemap, which shows the whole contents of the directory tree straight away; and the extension list, which serves as a legend and shows statistics about the file types. Some call this program “Disk Inventory X for Windows”

Open-Xchange Server 5 delivers more than users expect. The rich interface provides a dynamic new experience. Secure and robust, OX delivers the power to share email, calendar, contacts, tasks and documents. In fact, OX includes 11 collaboration modules, more than any other groupware product.
You can access OX from almost any browser, rich client, or mobile device. It puts your mission-critical data at your fingertips. Through “OXtenders”, Open-Xchange connects to proprietary and open source rich clients and PDA’s. Users already accustomed to Microsoft Outlook need not make any changes in their …

OpenOffice.org 2 is the leading open-source office software suite  for word processing, spreadsheets, presentations, graphics, databases and more. It is available in many languages  and works on all common computers. It stores all your data in an international open standard format and can also read and write files from other common office software packages. It can be downloaded and used completely free of charge for any purpose.

In December 2004 DD-WRT was founded by Sebastian Gottschall with the initial target that was just a modification of the original Linksys Firmware for supporting simple Radius Authentication. Gottschall then decided to add some more small tools and fancy things, just for fun. Out from the great response from the DD-WRT Community, after releasing it to the public, Gottschall developed more features and started also to redesign the complete firmware.
The Firmware features:

Virtual SSIDs
Virtual DHCP-Servers
PPTP over WAN
Bridging + VLAN support
VDSL Support
OpenVPN
IPv6 Support
and Many More…

Untangle has created one of the most impressive applications of this principle. The Untangle Gateway bundles together a list of applications that even seasoned sysadmins couldn’t install and effectively manage in a timely manner.
As the official name indicates, The Open Source Network Gateway, is open source. As with most commercial open source offerings, you must buy the Professional Package to get some features, but surprisingly few. All of the core functionality is included in the OSS version; enterprise management goodies augment the product for the Professional Package offering. – Charlie …

UltraVNC is a powerful, easy to use and free software that can display the screen of another computer (via internet or network) on your own screen. The program allows you to use your mouse and keyboard to control the other PC remotely. It means that you can work on a remote computer, as if you were sitting in front of it, right from your current location. If you provide computer support, you can quickly access your customer’s computers from anywhere in the world …