Sunbird - A Free Alternative To Microsoft Outlook (and Other Calendar Software)Mozilla's Sunbird is a free and open source choice to the calendar features of Microsoft Outlook. Sunbird is available on serveral operating systems, such as Windows, Linux, Mac OS, and Solaris.
Sunbirds lets you schedule events and tasks, and view them by day, week or month. Simple, but useful.
For a free replacement for the email features in Outlook, have a look at Mozilla Thunderbird.
An online alternative to Sunbird and MS Outlook is Google Calendar
if you are already using Thunderbird, download Lightning which brings the Sunbird calendar to Thunderbird.