Ok, so we use Outlook with Exchange, my phone is an iPhone and with the 2.0 update I can now sync to Exchange for mail and calendar (and contacts which I’m not doing).
The cool thing is that when you link to your Exchange calendar, you can view add and edit and changes (almost) immediately show up on the Exchange calendar.
The problem is that if you do that, it’s the only calendar you can have on your phone. Plus I use iCal on my Mac and Google Calendar from time to time… this post explains how I got around that and am now in calendar syncing bliss.
Basically the way I got everything working is I use Google Calendar as a back end for all my other calendars, meaning everything syncs to and from Google Calendar.
First iCal:
I use a program called BusySync, there is another app called Spanning Sync, but BusySync has MUCH better pricing. There is also Gcaldaemon, which is open source but kind of difficult to set up, let’s just say that that kind of app is why I don’t use Linux anymore, but if you can get it working more power to you! 
This app lets you select which iCal calendar you want to share with which Google Calendar, then set a schedule to tell it how often to sync.. it works VERY well.
Now Exchange / Outlook:
There is a free sync tool from Google, but it only lets you sync your primary calendar. In my case this is my work stuff that I do not want to mix with my personal stuff, so this didn’t work for me.
What I ended up using was gSyncit. This lets you pick any Outlook Calendar and sync it with any Google Calendar.
I just created a new calendar in Outlook, called ‘Personal’, and synced it with the same Google calendar that I synchronized iCal with.
iPhone:
The iPhone was easy. I just set up a new Exchange connection, selected to sync my mail and my calendar and that was it.
Now when I go to the calendar on the iPhone I can see my calendar for work stuff, the one I created for personal or appointments for both calendars.
The best part about this whole thing is everything is bi-directional.
What I mean is that if I update my calendar on my phone (essentially my exchange calendar) it will immediately show up in Outlook, then when gSycinit runs it will sync with Google calendar and then when BusySync runs it will sync with iCal… so basically within 5-10 minutes my update will show up on all my calendars!
This goes for any of the calendars, I can update any of them and it will update all the other calendars.. a beautiful thing!
