Open Source - Transparent Code

Open source is a design philosophy which means a lot of things depending on who you ask. To some, open source means free software, collaborative development, and full compliance with standards. For, others, open source means having open governance, freedom and advocacy. Either way, open source is a grass roots movement that is pretty much here to stay. Many of us use open source applications without knowing it! And best of all, some of the worlds most stable and secure operating systems are open source projects. Probably the best known open source project is Ubuntu. Whereas open source is usually non-commercial, Ubuntu made famous a great new open source paradigm - commercially supported open source projects! Feel free to add your own observation of best open source projects, websites or initiatives to this list. These can be global open source initiatives or local ones. Kindly add a summary for a domain that adds value to it.