Zimbra is an open source server and client technology for next-generation messaging and collaboration. Zimbra delivers innovation for both the administrator and the end-user as well as compatibility with existing infrastructure and applications (both open source and proprietary).
Hula is a calendar and mail server whose goal is to be fun and easy to use, while scaling effortlessly from small groups to large organizations with thousands of members. Hula is an open source project led by Novell (http://www.novell.com).