Chandler, the open-source PIM suite directed by Mitch Kapor (of Lotus 1-2-3 fame) is making progress. According to Oren Sreebny:

… there will be a 0.5 release in the first quarter of 2005 that will be designed to be usable for basic individual and collaborative tasks in a small workgroup - OSAF intends to adopt that release for their own uses, hence the nickname “dogfood” (as in “eat our own…”) for this release.

There’s also some discussion about collaborative calendaring:

We had a lot of discussion about whether it would make sense for OSAF to elevate the priority of adding calendaring client functionality (using CalDAV) earlier rather than later (that of course begged the question of who was going to build a CalDAV server). The prevailing sentiment in the group was that sounded like a good idea, but we wanted some more detail on the level of effort required and which other features were likely to be deferred to make that happen.

IMHO, workgroup collaboration, and especially calendaring, is the single biggest issue that the open source desktop people face. In most areas (Networking, email transport, email access, file transfer), the industry has adopted open protocols and open standards, and the result has been a huge amount of consumer choice. Calendaring has been the big exception–the only real standard there is Microsoft Exchange, and it leaves users with little to no choice at all. Strangely, the Internet community has failed to come up with a single solid calendar exchange protocol after over a decade of trying; hopefully this attempt will finally be successful.