Leopard iCal supports shared calendars.

http://apple.com/macosx/leopard/ical.html

I would suggest you take a look at Oracle Calendar. The Calendar Server is a part of Oracle's Collaboration Suite but can also run standalone. Oracle bought out Steltor a few years back because they liked Steltor's CorporateTime package and didn't feel like reinventing a perfectly round wheel. Oracle Calendar Server runs on Linux or Windows. Clients are available for Linux, OS X and Windows. There is even a plugin that allows MS Outlook to use Oracle Calendar instead of Exchange for calendaring and sync clients for Pocket PC and Palm handhelds (palm only on OS X). Oracle is a major backer of the CalDav standard and plans to support it in a future release of Oracle Calendar.
You can download the Client and Server for a free eval.

http://www.oracle.com/technology/products/ocal/index.html

Jay

If you don't have staff to manage ZImbra or Scalix, then avoid Oracle like the plague. It's much more difficult to install and manage than Zimbra, Scalix, Exchange, or even Lotus Domino.

I disagree. The initial install is a little ugly (You have to download the full Collaboration suite which over a gig). But once Oracle Calendar is up and running, it requires nearly zero maintenance. The only time I touch it is when we need to add or remove accounts. It's quite speedy to even on low end hardware. We originally had it on a 500mhz desktop

Jay

What about MeetingMaker?

http://www.meetingmaker.com/home.cfm

Zimbra's new release will work for you, but if your Mac users are also MS Office users, you can use MS Exchange very nicely. Or, of course, wait for leapord.

Certainly, Kerio Mail Server should be worth taking a look at. It is quite robust-a very good alternative to Exchange. Very good feature set. Nice web mail client. (www.kerio.com)

OK-I checked out the following:
Oracle--too much admin needed
MeetingMaker--doesn't do iCal integration
Zimbra-yes, just need the iSync to work
Kerio-will run on Mac but doesn't seem to do much with iCal

Honestly, the open standards approach to calendaring is not there yet. Hopefully, the release of Apple's free CalDAV server http://trac.macosforge.org/projects/calendarserver will help jump start the CalDAV parade of support. Oracle's server will (does?) support CalDAV, and there are other OSS CalDAV servers (Cosmo and Bedework come to mind) out there. However, until the critical mass of supporting clients are available, you will be stuck with a non-interoperable solution, like Exchange, Domino, MeetingMaker, Oracle CS, etc.

As regards syncing, I feel that this is just a band aid until we get to the open standard, client/server based model. Syncing is just someone with more organization than you or I copying items from one client to another.

Right now, we are where email was 20 years ago, with proprietary client and servers.Hopefully, that is about to end.

Why not just forget about ical and use the google calendar instead?

I have used http://www.icalx.com/ for three years now, and in spite of the non-activity on the site itself, the "publish" function has worked flawlessly.

Kerio MailServer is Cheap(ish) under 300 sterling and a dream to configure, solid and feature rich http://www.kerio.com

We've been testing Zimbra, using their sync conduit/system pref, and it has worked fine with iCal, even syncing to Palm PDAs. This was with v 3.2 (or was it 3.0?), have not tried it with 4.0 yet.

They did break some things in 3.2 that worked previously.

Once set up, it seems to work fine with no meddling from us, other than to tweak settings to our liking, or do some testing. I'd keep Zimbra on the top of your list.

I've been chewing on this one a bit lately too. Our office has Mac, Windows and Linux represented and we're way too small to implement anything other than a very low-cost, no-cost solution.

Google's Calendar is soooo close to being workable. If only it had true two-way sync'ing with anything (Outlook, iCal, Sunbird).

I've been following the progress of Mitch Kapor's Chandler and the Cosmo Sharing Server (though haven't tried implementing).
http://chandler.osafoundation.org/

But honestly, I think Apple will release their calendar server first. The whole thing is frustrating to say the least.

Yeah, Chandler is there in theory but not practice. Maybe Google will deliver?

I don't really want to have to run a dedicated calendar server--especially when you consider the price of Mac hardware.

I run a shop of about 50 macs, (ad agency) and we have an exchange server. entourage 2004 has become more or less a full fledged exchange client, it works well.

what doesn't work can be worked around in OWA.

For those who do use an Exchange-based server at the office, for example, then Snerdware's Groupcal is a godsend -- works well (READ the installation instructions for best results!) and nearly trouble-free. This has allowed me to use a Mac in a situation that would otherwise have been quite problematic.

Setting up a Webdav server for iCal is superior straightforward and doesn't require OS X Server. Though I have set up Webdav on OS X Server and iCal sharing works extremely well. Google setting up Webdav in OS X client for iCal use. Actually any Webdav will work.

XC Connect
http://www.xcnetwork.com/index.jsp
From XChange Network

Multiplatform calendaring, Mac, Windows, and Linux. As an independent consultant to the SOHO market, I've found XC Connect to provide groupware, multiplatform calendaring using the native applications on each platform. Entourage or the iCal and Address Book combination on Mac, Outlook on Windows, and Evolution on Linux.

Permits syncing with Palm devices and smartphones as well. It's not without flaws, but recommend it.

Open-Xchange Server may offer what you're looking for. It offers POP and IMAP email support, WebDav, and supports quite a number of client environments. People using Windows, Linux, Mac OS, PalmOS and others have been able to collaborate with one another using Open-Xchange.

May I suggest you visit www.open-xchange.com and check it out?

Dan Kusnetzky

Anyone familiar with Happy Jack software and their product, Calibrate Groups?

http://www.happyjacksoftware.com/

Sounds like Google Calendar is almost what you need. We've got a set of open APIs and a number of third parties that have delivered sync solutions. We're also working on sync with various desktop and mobile clients -- hope to have something to share before too long.

http://sourceforge.net/projects/jscalendarsync

Allows to synchronize Apple's iCal with Sun Microsystems's Java System Calendar Server data using Mac OS X native synchronization mechanism (iSync)

Also avaiable is a php script for proxy to Sun calenader that allow subscriptions from iCal.
http://rulink.rutgers.edu/macical.html

Happy Jack's group calendar really does everything you are speaking of. It has an API that one can use, it has widgets and it truly syncs with ical on the macs. They have a complete document on how to sync with macs on their web page.

Their sync tool (CALsync) is in beta.

Furthermore, they have a FREE version for the family (five users).

You can sign up for a 30 day free trial of the CALibrate Groups.

I use CALibrate Groups and a Mac. As a professor, I want my students to know my schedule so they can come visit me during office hours. It almost works -- they still send me email asking. But the integration between CALibrate and Mac's iCal is great.

This works in the latest version of Zimbra. See our blog post on this, also note you can get a free trial, and instant activation: Zimbra hosting provider 01.com: http://www.01.com

http://blog.01.com/?p=339

Thanks for your consideration.