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.
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
Gmail is a web-based email with very user-friendly interface and huge storage capacity
A free web-based calendar.
Google is the quintessential search engine.
Desktop spreadsheet and data analysis application.
Project and resource management software.