Hosted
n/a
Google
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.
Full-featured open source office productivity suite, featuring word processor, spreadsheet, presentation, drawing and database packages; free MS Office replacement.
Web-based project management tool
Web-based CRM that donates licenses to nonprofits
Email marketing/newsletter tool that tracks open rates, click-throughs, etc, segmentation support, and an "infinite" number of lists.