You're an open source shop.. how do you do shared calendaring? [closed]
Solution 1:
We use Google Calendar in our team, being all linux & mac guys. Otherwise the best common suggestion I've seen is Apple's calendar server:
http://trac.calendarserver.org/
Solution 2:
Check out webcalendar. I think it meets all of your requirements, and all but the mobile option of your nice-to-haves. I haven't used LDAP integration (although it's listed as supported) or delegation, so be sure to check that.