The "de facto standard for mail gateway scanning," ClamAV is a set of command line tools for protecting networks from malware. The same software is also available for the Windows desktop through a paid program called Immunet that can be downloaded from the same site. Operating System: Linux
Used by educational institutions and enterprises in 93 countries, Claroline includes tools for writing online course descriptions, delivering online course content, creating exercises, maintaining wikis, publishing announcements and more. It's won numerous awards, and it's available in 35 different languages. Operating System: Windows, Linux, OS X
More than 73,000 sites have registered their versions of Moodle, and they offer nearly 6 million online classes that reach more than 58 million students. It's a full-featured e-learning platform that aims to give educators "the best tools to manage and promote learning." Operating System: Windows, Linux, OS X
School budgets are getting tight, and openSIS saves most schools about 75 percent compared to commercial alternatives. It's reliable, scalable, and includes most of the features you would find in software like PowerSchool. In addition to the free community version that's suitable for smaller schools, it also comes in commercially supported school and district editions. Operating System: Windows
Designed for schools in the developing world, this student information system offers a Web-based system for tracking attendance, grades, demographics and more. It runs on a Ubuntu Linux server, and can also be deployed in the cloud. Operating System: Linux
This multi-function server software includes anti-malware, anti-spam, mail server, content filter, stateful firewall, VPN, WAN, file and print sharing, groupware, Web filter and other capabilities. In addition, paid support, pre-configured hardware and other services are available from ClearSDN. Operating System: Linux
Like ClearOS, Zentyal can serve as a gateway, infrastructure manager, unified threat manager, office server and/or unified communication server. Subscriptions, support, training, add-ons and other services are available for a fee. Operating System: Linux
Describing itself as "the same kind of editing suite that the big boys use," Cinelerra encourages users to "unleash the 50,000 watt flamethrower of content creation in your UNIX box." Note that a community fork of the project can be found atCinelerra.org. Operating System: Linux
This video editor is very popular with Linux users and has been frequently featured in various Linux-related magazines. Key features include compositing, overlays, 3D animated titles, unlimited tracks and layers, scrolling credits, rotoscoping support, digital zoom and much more. Operating System: Linux
This cross-platform player supports most multimedia files as well as DVD, Blu-Ray, Audio CD, VCD, and various streaming protocols. It's simple, powerful, fast and very popular with open source aficionados. Operating System: Windows, Linux, OS X, others
Designed for home theater PCs (HTPCs), this award-wining multimedia player also plays most types of files. It also supports most remote controls, and it automatically creates a personal library of your audio and video files. Operating System: Windows, Linux, OS X.
Award-winning DansGuardian uses phrase matching, PICS filtering, URL filtering to block objectionable content on your network. Note that this is not software for protecting an individual PC—to use it, you need a server. Operating System: Linux, OS X
One of the younger projects on our list, BlueGriffon offers a WYSIWYG Web editor powered by the same Gecko engine that runs Firefox. It offers an intuitive interface for building sites that conform to the latest Web standards. Operating System: Windows, Linux, OS X
With an interface very similar to what you'll find on Dreamweaver, KompoZer makes it easy for anyone to create Web pages, even if you don't have a lot of technical knowledge. Key features include a WYSIWYG editor, integrated file management via FTP, HTML mode, tabbed editing, forms support and more. Operating System: Windows, Linux, OS X
One of the ways around the issues of security and control that make some businesses wary of cloud computing is to build a private cloud -- one that remains within the corporate firewall and is wholly controlled internally. Private clouds also increase the agility of IT an organization's IT infrastructure and make it easier to roll out new technology projects. Download this eBook to get the facts behind the private cloud and learn how your organization can get started.