Open Source is simply defined as a collaboration, predominantly online, whereby source code and software is made available under an open licensing structure with the aim of encouraging other developers and users to test it, tweak it and develop it further, reposting their achievements back to the community so that others can benefit from it.

What this actually means is that most generally available commercial software has an Open Source alternative – with the added benefit that these are available freely for anyone to download from the Internet.

Some of the good Open Source software available includes: WordPress, Joomla, Star Office, Open Office, Freemind… these are the obvious ones that spring to mind, that I’ve used, but there are far more!

Wikipedia define Open Source as:

Open source describes practices in production and development that promote access to the end product’s source materials—typically, their source code. Some consider open source a philosophy, others consider it a pragmatic methodology. Opening the source code enabled a self-enhancing diversity of production models, communication paths, and interactive communities. Subsequently, a new, three-word phrase “open source software” was born to describe the environment that the new copyright, licensing, domain, and consumer issues created.

 A main principle and practice of open source software development is peer production by bartering and collaboration, with the end-product (and source-material) available at no cost to the public.

Source: http://en.wikipedia.org/wiki/Open_source

A good list of available Open Source software (top 20)  is available from Trip Wire magazine, HERE.