OT: Is there a DECENT cross-platform calendaring server out there?

[Doug Stewart <dstewart atl lmco com>]

This is probably a bit off-topic, but I'm pretty close to pulling my 
hair out over this one.

My company and I are currently using a vastly-inferior calendaring 
program called Meetingmaker and desperately need to move to something 
that gives us a full-featured company calendaring solution without all 
sorts of extra cruft (read: file sharing, task tracking, webmail, etc.). 
 I've looked at OpenGroupware.org, Open Exchange, Oracle Calendar, Hula 
Server, Sun Calendar and a whole slew of web-based calendars from 
Freshmeat.  None of them are anywhere close to what we need.

We need cross-platform rich clients (OSX, Sun, Windows and Linux), asset 
reservation capabilities, proxies/assistants for administrative 
assistants and sync'ing with Palms at the minimum.

Anyone have any suggestions?  An F/OSS solution would definitely be 
preferable, but we can pay if need be.
--
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Doug Stewart
Systems Administrator/Web Applications Developer
Lockheed Martin Advanced Technology Labs
dstewart atl lmco com