To do so, go to Entourage -> Preferences -> General Preferences -> Sync Services. From here, enable the options to synchronize contacts and events with Address Book, iCal and .Mac (MobileMe).

This is what I've done and it works pretty well overall. Except for one persistent and annoying problem: My calendar appointments inevitably begin to reproduce. That is, at some point, I'll find two of every calendar event in Entourage. At the same time, iCal will show a matching set of duplicates. This replication process expands over time, so that older appointments (once I have saved past their due date) often wind up with four or six copies.

Who's to blame for this bug? There is some dispute (see for example) as to whether the cause lies primarily with Microsoft Office or with Leopard's Sync Services software. Personally, I give the nod to Microsoft, as I have never had the problem in iCal unless I am syncing iCal with Entourage. What is undisputed is that there is not yet a permanent fix. Neither Apple nor Microsoft appear to be in a hurry to correct the situation.

What can you do in the meantime? Your choices are limited. Either give up on using Entourage for syncing or keep deleting the duplicates as you find them. The latter option can be a time-consuming nuisance, especially if you have a lot of duplicates. If so, try this procedure to eradicate the unwanted copies with a minimum of fuss:

However, when I tried this, and waited about 30 minutes, nothing happened. Growing impatient for results, I tried something else.