Another vote for Google Calendar. I have it set up in iCal (already installed on your Macbook Air). That way, whenever I make changes in iCal they sync with Google Calendar, which then syncs with my iphone, and vice versa.
For syncing contacts, I use the address book that comes preinstalled (although I do not have anything set up to sync changes wirelessly like with my calendar, never really needed it). In itunes there is an option to sync your iphone with the "Address Book" app.