Localization
Very extensible CMS platform based on PHP and used by many NGOs - "Community Plumbing"
Firefox is the popular open source web browser from Mozilla
Free/cheap Internet telephony and handy IM tool.
Web based social bookmarking lets you share online finds and discover new ones. Ground zero for tagging.
Open source constitutent relationship management system.
Powerful wiki software built to support the Wikipedia project
A Free Telnet/SSH Client
URL-shortener (for emailing and general usability)
Web-based CRM that donates licenses to nonprofits
Social networking for non-social purposes with a focus on professional development, networking for jobs and problem solving through the expertise of those in your extended network.
Inexpensive antivirus software for up to five computers.
Gmail is a web-based email with very user-friendly interface and huge storage capacity
web-based interface for managing MySQL
Social networking tool