This document provides an overview of open source software that can be used by non-profit organizations. It discusses popular open source operating systems like Linux and BSD and describes commonly used server software such as Samba, Mailman, LAMP stacks, and content management systems. It also mentions desktop applications like Mozilla Suite, Firefox, Thunderbird, OpenOffice, and GIMP. The document notes that while over 60% of non-profits use open source on their web servers, only around 20% use it as their desktop operating system. Barriers to adoption include familiarity with proprietary tools and lack of support and expertise.