I've got a web app I'm working on that allows users to view conference rooms and reserve rooms for certain days/times. We are wanting to add a "calendar" link that the user can click on for an event that is scheduled and add that event to their Outlook or G-mail calendar. That's not the tricky part. The tricky part is if an event is modified in any way (time changed, cancelled, location changed, etc) everyone who has "subscribed" to that event in their calendar should have their calendar event automatically updated. The guy who started coding this web app kept telling everybody he was going to use iCal. Unfortunately, he's not around anymore for me to ask questions of and he never actually started coding anything for this even though he told people he was almost done with it. I've looked at iCal and from what I can tell it is a Windows-based calendar server with a web front end. We are a Linux/java shop and I need something that has a web service to interface with from my java web app. Has anybody done something like this and have any recommendations?