Flexible open-source content management and blogging software with an active user and developer community and a wide variety of plug-ins or extensions available.
Firefox is the popular open source web browser from Mozilla
Rich client application for editing a full range of web content, from simple HTML pages to PHP and other dynamic content formats
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.
Web-based project management tool
Web based photo sharing service
Gmail is a web-based email with very user-friendly interface and huge storage capacity
Google is the quintessential search engine.