Book excerpt: This is a compilation of 14 case studies on the successful deployment of free and open source software (FOSS) in select projects from Africa, Asia-Pacific, Europe and Latin America. In each case study, the reasons for choosing to use FOSS together with the development, implementation, and impact of the FOSS applications are discussed. The benefits obtained and challenges encountered as well as any valuable lessons learned are also highlighted. This books aims to provide policy makers and development practitioners with useful insights as to why FOSS may be more suitable than proprietary software for use in information and communications technology (ICT) development, especially in poorer economies.