Apple's iCal lets you make a calendar available to others by "publishing" it, but subscribers can't edit your published calendars. And although MobileMe members can sync calendars among Macs and make changes on any of them, this only works if each Mac is logged in with the member's MobileMe ID. If you want family members or coworkers to be able to see and edit your iCal calendars, BusyMac's BusySync 2.1.6 may be just the tool you need. It syncs calendars among Macs (with the same or different users), among user accounts on a given Mac, and between your Mac and Google Calendar--in any combination.

Setup is somewhat involved. After installing the BusySync preference pane and turning it on, you must make a series of choices. For each iCal calendar on your Mac, decide whether you want to publish it and, if so, whether you want to require subscribers to enter a password to read it, make changes to it, or both. You can also subscribe to calendars on other Macs on your local network (or--with some extra manual fiddling--elsewhere on the Internet), optionally filtering out to-do items and alarms. And finally, you can connect to your Google Calendar account, both publishing calendars from your Mac and subscribing to existing Google calendars. (Although Google Calendar now supports CalDAV, meaning you can connect directly to your Google calendars with the Leopard version of iCal, BusySync provides better ease of use and more flexibility. For example, there's currently no way to get read-write access to a CalDAV calendar on an iPhone or iPod touch, but calendars synced using BusySync don't have this limitation.)

A given calendar may be connected in multiple ways--for example, you may subscribe to a Google calendar and also publish it on your local network--but BusySync can't merge the contents of an existing iCal calendar with an existing Google calendar; that requires several manual steps. BusySync is also compatible with MobileMe, so that (in theory at least) your Mac, the MobileMe Web site, Google Calendar, and your iPhone all get updated when a change happens on any one of them. Of course, this requires that you have everything configured just so; that your computer is on and BusySync is running; and that you wait long enough after any given change for two or more separate syncing operations to occur.

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