ZCS 3.0 Beta 3 (aka Milestone 3) has been released. You can get the Open Source Edition from the downloads page. The Network Edition is available for a 60 day free trial. Current Network customers or trial participants can get the latest release from the support portal.
New features of the Zimbra Collaboration Suite 3.0 Beta 3 Open Source Edition include: redesign of the filters UI, a one-click "Check Mail" button, the ability to reply to an email and retain attachments, the ability to drag an email to mini-calendar to create an appointment based on the email, wild card searches, a new Outlook PST import utility, and migration from Exchange 5.5 servers. New features of the Network Edition include the ZCS Connector for Outlook (2003) and the ability for a global administrator to delegate domain-level administrators (whose only privileges are managing accounts within a single domain).