Firefox is a great product on its own, but if you need a full blown internet suite, you might want to have a look at the following Firefox companions from the Mozilla family of free, cross platform, open source products:
Email application: Mozilla Thunderbird
Like its Firefox brother, Thunderbird has automatic software updates, extensions and themes customizations. Thunderbird has the important features for business types too: spell checking, good address book, strong searching capabilities, attachment management (you can delete them and keep the email message in your archives) and built-in RSS capabilities. If you're afraid of changing programs, don't be, Thunderbird will import all your previous address book and emails from a wide selection of email softwares.
Calendar application: Mozilla Sunbird
Sunbird is a practical calendar application and personal information manager based on the open iCalendar standard. It will help you with national holidays and other personal reminders. It also contains a task list for things to do that may not have a precise date to it. The interface is user friendly and you can decide the type of view you prefer based on a time scale, such as daily, weekly or monthly views. Finally, you can subscribe to all kinds of online calendars, whether you are following a particular sport team or international holidays.
Web authoring application: KompoZer
KompoZer is an Open Source project based on the old NVU application and was started from the Mozilla Composer code base. KompoZer is a complete Web Authoring System that combines web file management and easy-to-use WYSIWYG web page editing, like FrontPage and Dreamweaver. KompoZer is designed to be extremely easy to use, making it ideal for non-technical computer users who want to create an attractive, professional-looking web site without needing to know HTML. Even though it's designed for the novice web designer, KompoZer is also beneficial for experienced web programmers who want to save time in web design.