Alberto Escudero writes "The "VoIP-4D Primer" is a free guide available in four major languages (english, french, arabic and spanish) under Creative Commons. The booklet is an effort to disseminate the use of telephony over the Internet in developing regions.
The 40-page guide targets both technical and non-technical readers. The first part presents the essentials of telephony over the Internet. For those interested in the more technical details, hands-on guidelines and configuration files are included in the second part. The examples provide essential background to build your own low-cost telephony system.
More info, media coverage and free PDF downloads are available here: http://voip4d.it46.se/"