Firefox is the popular open source web browser from Mozilla
Full-featured open source office productivity suite, featuring word processor, spreadsheet, presentation, drawing and database packages; free MS Office replacement.
Web based photo sharing service
Wikipedia is a global and multilingual Web-based cooperative free-content encyclopedia.
Free, Open dynamic web mapper. (An alternative to Google/Yahoo Maps)
industry standard open source web server
The open source GIS platform, powerful and cross platform
OpenStreetMap is a project aimed squarely at creating and providing free geographic data such as street maps to anyone who wants them.
Open source database.
Free/Open Source Mapping and GIS Analysis software for Linux, OS X and Windows. Comparable to Manifold or ArcView