If you're using BES 4 then you can wirelessly sync to Exchange, and use Entourage on the Mac to access the same mail / calendar. The latest versions of Exchange also have a web client. If you don't want to host BES, then there are various online hosting companies that you can use (that maintain Exchange and BES).
The other way is to use PocketMac (http://www.pocketmac.com)
. This is an application that is installed on your Mac to sync the built in applications (iCal, Address Book, Stickies) with your BB. PocketMac can also sync Entourage and Daylight. That will keep the Mac and BB in sync. To publish calendars in iCal you can either use Apple's .Mac service (http://www.mac.com)
, set up a WebDav server with PHP iCalendar (http://hcs.harvard.edu/~westin/phpicalendar.php
) or use a third party solution such as iCal Exchange (http://www.icalx.com/
) or iCal share (http://icalshare.com/)