If you're looking for an alternative to the large, incumbent groupware packages but don't want to uproot anything, take a look at Scalix's Community Edition for Linux. The free Community Edition has most of the features of its Enterprise sibling with the notable exceptions of Outlook integration, group calendar, and shared folders. That said, you do get an e-mail server, personal calendar and contacts, and Web access among other things. It supports unlimited "Community" users and five Scalix Enterprise Edition user licences. Upgrading to the full Enterprise Edition is then an option.
Price: Community Edition is Free, $92.40 per user for the Enterprise Edition (maintenance is $16.70 per user per year)
Availability: Now through Custom Technology
URL: www.scalix.com, www.customtech.com.au