The Open Source Initiative is an excellent portal for learning about Open Source.

The Nonprofit Open Source Initiative provides non-technical primers regarding Open Source.

The International Open Source Network, an initiative of the United Nations Development Programme, has a plethora of cagegorized Open Source resources.

The Open Source Reference Book is an essential reference containing the who's who and who's doing what in Open Source.

NewsForge is the online newspaper for Open Source.

Open Sources: Voices from the Open Source Revolution is available for on-line reading from O'Reilly.

The UNESCO Free Software Portal is a comprehensive resource for global resources on Open Source.