Bedework is popular at universities, mainly because it easily deals with multiple calendars per user and talks to everything but Exchange clients (which is squarely in their plans).
It may be a bit over-the-top for a small company's needs. -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
